ci: build OCCT shared on Linux so plug-ins share one OCCT instance

`geom.tree().select()` silently returns zero results (or raises SWIG's
"An unknown error occurred") in the Linux release packages, while the same
commit built from source returns correct answers. `select_box()` agrees
between both, and geometry conversion is bit-identical -- only operations
that touch a stored TopoDS_Shape diverge.

Cause is linkage, not code. 8bdaa8c7c narrowed the Rocky builds from
`--shared` to `--ifcopenshell-shared`, which shares IfcOpenShell's own
libraries but leaves every dependency static. OCCT is then compiled
privately into each plug-in that uses it -- 15 of them, verified by their
own copies of the BRepClass3d/BRepExtrema/Standard_Failure strings.

That contradicts what the binaries already declare. tree.h:1748 casts a
`conversion_result_shape*` to `open_cascade_shape*`, moves the
TopoDS_Shape out of it and frees it; `open_cascade_shape` is defined once
in ifcopenshell_geometry_kernel_opencascade.so and left undefined in
ifcopenshell_geometry_tree_opencascade_brep.so for the loader to resolve.
So the two plug-ins are designed to share one OCCT-based type system, yet
static linking gives each its own Standard_Type registry and allocator.
Shapes get read and released by a different OCCT instance than made them.

Add `--opencascade-shared`, mirroring the existing `--ifcopenshell-shared`
precedent, and use it on both Rocky workflows. It cannot be spelled
`--occt-shared`: build-all.py parses any `occt-*` flag as a version
override.

BUILD_STATIC drives three things at once -- dependency link type,
-fvisibility=hidden, and BUILD_SHARED_LIBS -- so making one dependency
shared means overriding all three for it. Visibility is the subtle one:
OCCT's Standard_EXPORT expands to nothing on Unix, so it relies on default
visibility to export its API. Built shared under -fvisibility=hidden it
exports almost nothing and its own libraries cannot resolve against each
other (libTKMath.so fails to find
NCollection_BaseAllocator::CommonBaseAllocator in libTKernel.so). Static
archives are immune, which is why this surfaces only once OCCT goes
shared. Compile OCCT with the pre-visibility flag set instead.

Put the shared OCCT on LD_LIBRARY_PATH for the build itself. Nothing else
points at it -- IfcOpenShell's libraries get INSTALL_RPATH=$ORIGIN and OCCT
sits in its own dependency prefix -- so the post-build `import ifcopenshell`
check fails with "libTKernel.so.7.8: cannot open shared object file". This
is build-time only; the shipped packages get libTK*.so* staged beside the
payload with an $ORIGIN RUNPATH instead.

Suffix OCCT's install directory with `-shared` when it applies. Static and
shared installs are not interchangeable, but `build_dependency` skips any
dependency whose install dir already exists and cache_dependencies.py keys
its tarballs purely on that directory name -- so the static
`cache-occt-7.8.1.tar.gz` restored from the build-outputs repo silently
satisfied the build and BUILD_LIBRARY_TYPE was never applied. This is the
same cache stickiness 8bdaa8c7c described, pointing the other way. The
suffix makes the key configuration-aware, so it self-invalidates and the
static tarball stays valid for builds that still want static.

Packaging is the other half, and is why 8bdaa8c7c backed the flag out --
`stage_runtime_payload` only copies from install/ifcopenshell, so OCCT in
install/occt-* was never staged and `--shared` "worked by accident" off
cached static outputs. Stage libTK*.so* alongside, then give every staged
library an $ORIGIN RUNPATH: the core libs currently carry dead
build-machine RPATHs and the plug-ins carry none, resolving only because
the Python wrapper pulls them in by SONAME first. Shared OCCT has no such
first loader, since it is reached through the dlopen'd plug-ins.

This shrinks the packages. Duplicated OCCT is 113 MB of the 287 MB
unpacked python payload (the eight geometry_writer_ifc* plug-ins alone are
4.6 MB each); one shared copy of the 29 linked libTK is around 67 MB, and
the plug-ins collapse to source-build sizes -- kernel_opencascade 15.4 MB
-> 1.2 MB, tree_opencascade_brep 9.6 MB -> 248 KB. Same argument as
a91b1da28 ("Reduce Rocky package size") and 402591e71.

macOS and Windows are affected too but are not fixed here. Their
packaging resolves via @loader_path install names and would need
install_name_tool rewriting, which cannot be verified from Linux; adding
the flag without that would ship a package that fails to load.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/workflows/build_rocky.yml

@@ -80,7 +80,7 @@ jobs:
           set -o pipefail
           CXXFLAGS="-O3" CFLAGS="-O3" ADD_COMMIT_SHA=1 BUILD_CFG=Release BUILD_BONSAIVIEWER=ON \
             uv run --with aqtinstall ./nix/build-all.py \
-            -v --diskcleanup --ifcopenshell-shared 2>&1 \
+            -v --diskcleanup --ifcopenshell-shared --opencascade-shared 2>&1 \
             | tee build.log
 
       - name: Upload Build Logs
@@ -147,6 +147,22 @@ jobs:
               done
           }
 
+          # Copy the shared OCCT from the dependency prefix to the provided `$1`.
+          # OCCT is built shared (`--opencascade-shared`) so that the opencascade kernel
+          # and tree plug-ins share a single OCCT instance: `open_cascade_shape` objects
+          # are created by the kernel plug-in and then have their `TopoDS_Shape` moved out
+          # and freed by a tree plug-in. A private static OCCT per plug-in gives each its
+          # own Standard_Type registry and allocator, which silently corrupts those shapes.
+          # These libs live under `install/occt-*` rather than `install/ifcopenshell`,
+          # so `stage_runtime_payload` does not pick them up on its own.
+          stage_occt_runtime_payload() {
+              dest="$1"
+              for occt_lib_dir in "$(dirname "$install_root")"/occt-*/lib "$(dirname "$install_root")"/occt-*/lib64; do
+                  [ -d "$occt_lib_dir" ] || continue
+                  find "$occt_lib_dir" -maxdepth 1 \( -type f -o -type l \) -name "libTK*.so*" -exec cp -P {} "$dest/" \;
+              done
+          }
+
           # Copy all libs from `install/ifcopenshell` to the provided `$1`.
           # Set `$2` to `0` to skip including geometry writers.
           stage_runtime_payload() {
@@ -163,7 +179,14 @@ jobs:
                       find "$runtime_dir" \( -type f -o -type l \) \( -name "*.so" -o -name "*.so.*" -o -name "*.dylib" -o -name "*.dll" \)
                   done
               )
+              stage_occt_runtime_payload "$dest"
               ensure_soname_links "$dest"
+              # The core libs ship with dead build-machine RPATHs and the plug-ins have
+              # none; today they resolve only because the Python wrapper ($ORIGIN) pulls
+              # them in by SONAME before any plug-in is dlopen'd. Shared OCCT has no such
+              # first loader -- it is reached through the plug-ins -- so give every staged
+              # library an $ORIGIN of its own.
+              find "$dest" -maxdepth 1 -type f -name "*.so*" -exec patchelf --set-rpath '$ORIGIN' {} \;
           }
 
           # Copy all libs from `QT_DIR` to the provided `$2`.

.github/workflows/build_rocky_arm.yml

@@ -92,7 +92,7 @@ jobs:
           set -o pipefail
           CXXFLAGS="-O3" CFLAGS="-O3" ADD_COMMIT_SHA=1 BUILD_CFG=Release BUILD_BONSAIVIEWER=ON \
             uv run --with aqtinstall ./nix/build-all.py \
-            -v --diskcleanup --ifcopenshell-shared 2>&1 \
+            -v --diskcleanup --ifcopenshell-shared --opencascade-shared 2>&1 \
             | tee build.log
 
       - name: Upload Build Logs
@@ -156,6 +156,22 @@ jobs:
               done
           }
 
+          # Copy the shared OCCT from the dependency prefix to the provided `$1`.
+          # OCCT is built shared (`--opencascade-shared`) so that the opencascade kernel
+          # and tree plug-ins share a single OCCT instance: `open_cascade_shape` objects
+          # are created by the kernel plug-in and then have their `TopoDS_Shape` moved out
+          # and freed by a tree plug-in. A private static OCCT per plug-in gives each its
+          # own Standard_Type registry and allocator, which silently corrupts those shapes.
+          # These libs live under `install/occt-*` rather than `install/ifcopenshell`,
+          # so `stage_runtime_payload` does not pick them up on its own.
+          stage_occt_runtime_payload() {
+              dest="$1"
+              for occt_lib_dir in "$(dirname "$install_root")"/occt-*/lib "$(dirname "$install_root")"/occt-*/lib64; do
+                  [ -d "$occt_lib_dir" ] || continue
+                  find "$occt_lib_dir" -maxdepth 1 \( -type f -o -type l \) -name "libTK*.so*" -exec cp -P {} "$dest/" \;
+              done
+          }
+
           stage_runtime_payload() {
               dest="$1"
               include_geometry_writers="${2:-1}"
@@ -170,7 +186,14 @@ jobs:
                       find "$runtime_dir" \( -type f -o -type l \) \( -name "*.so" -o -name "*.so.*" -o -name "*.dylib" -o -name "*.dll" \)
                   done
               )
+              stage_occt_runtime_payload "$dest"
               ensure_soname_links "$dest"
+              # The core libs ship with dead build-machine RPATHs and the plug-ins have
+              # none; today they resolve only because the Python wrapper ($ORIGIN) pulls
+              # them in by SONAME before any plug-in is dlopen'd. Shared OCCT has no such
+              # first loader -- it is reached through the plug-ins -- so give every staged
+              # library an $ORIGIN of its own.
+              find "$dest" -maxdepth 1 -type f -name "*.so*" -exec patchelf --set-rpath '$ORIGIN' {} \;
           }
 
           stage_qt_runtime_payload() {