diff --git a/nix/build-all.py b/nix/build-all.py
index 937462a45c..0aea75b82c 100644
--- a/nix/build-all.py
+++ b/nix/build-all.py
@@ -801,12 +801,13 @@ LDFLAGS = os.environ.get("LDFLAGS", "")
 
 ADDITIONAL_ARGS_STR = " ".join(ADDITIONAL_ARGS)
 
+CXXFLAGS_MINIMAL = f"{CXXFLAGS} {PIC} {ADDITIONAL_ARGS_STR}"
+CFLAGS_MINIMAL = f"{CFLAGS} {PIC} {ADDITIONAL_ARGS_STR}"
 if "wasm" in flags:
-    CFLAGS_MINIMAL = CXXFLAGS_MINIMAL = CFLAGS = CXXFLAGS = os.environ["SIDE_MODULE_CFLAGS"]
-    LDFLAGS = os.environ["SIDE_MODULE_LDFLAGS"]
+    # WASM `SIDE_MODULE_` are absorbed by `emcmake` automatically.
+    CXXFLAGS = CXXFLAGS_MINIMAL
+    CFLAGS = CFLAGS_MINIMAL
 elif sp.call([bash, "-c", "ld --gc-sections 2>&1 | grep -- --gc-sections &> /dev/null"]) != 0:
-    CXXFLAGS_MINIMAL = f"{CXXFLAGS} {PIC} {ADDITIONAL_ARGS_STR}"
-    CFLAGS_MINIMAL = f"{CFLAGS} {PIC} {ADDITIONAL_ARGS_STR}"
     if BUILD_STATIC:
         CXXFLAGS = f"{CXXFLAGS} {PIC} -fdata-sections -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden {ADDITIONAL_ARGS_STR}"
         CFLAGS = f"{CFLAGS}   {PIC} -fdata-sections -ffunction-sections -fvisibility=hidden {ADDITIONAL_ARGS_STR}"
@@ -815,8 +816,6 @@ elif sp.call([bash, "-c", "ld --gc-sections 2>&1 | grep -- --gc-sections &> /dev
         CFLAGS = CFLAGS_MINIMAL
     LDFLAGS = f"{LDFLAGS}  -Wl,--gc-sections {ADDITIONAL_ARGS_STR}"
 else:
-    CXXFLAGS_MINIMAL = f"{CXXFLAGS} {PIC} {ADDITIONAL_ARGS_STR}"
-    CFLAGS_MINIMAL = f"{CFLAGS}   {PIC} {ADDITIONAL_ARGS_STR}"
     if BUILD_STATIC:
         CXXFLAGS = f"{CXXFLAGS} {PIC} -fvisibility=hidden -fvisibility-inlines-hidden {ADDITIONAL_ARGS_STR}"
         CFLAGS = f"{CFLAGS}   {PIC} -fvisibility=hidden -fvisibility-inlines-hidden {ADDITIONAL_ARGS_STR}"