vs-cfg: remove VS_HOST / VS_TOOLSET_HOST

They were added awhile ago in 67666ed for overcoming some win32 issues, which is not around anymore.
And now `VS_HOST` is never set (and therefore `VS_TOOLSET_HOST` is always empty too) and likely to be never used.

win/build-deps.cmd

@@ -1035,11 +1035,7 @@ pushd %BUILD_DIR%
 :: cache always e.g. when we've had new changes in the repository.
 IF %BUILD_TYPE%==Rebuild IF EXIST CMakeCache.txt. del CMakeCache.txt
 
-set VS_TOOLSET_CMAKE_ARG=
-IF NOT "%VS_TOOLSET_HOST%"=="" (
-    set VS_TOOLSET_CMAKE_ARG=-T %VS_TOOLSET_HOST%
-)
-set COMMAND=cmake .. -G %GENERATOR% -A %VS_PLATFORM% %VS_TOOLSET_CMAKE_ARG% %*
+set COMMAND=cmake .. -G %GENERATOR% -A %VS_PLATFORM% %*
 echo %COMMAND%
 %COMMAND%
 set RET=%ERRORLEVEL%

win/run-cmake.bat

@@ -197,11 +197,7 @@ if defined USE_NINJA (
     set ARCH_OPTION=-A %VS_PLATFORM%
 )
 
-IF NOT "%VS_TOOLSET_HOST%"=="" (
-    set VS_TOOLSET_OPTION=-T %VS_TOOLSET_HOST%
-)
-
-cmake.exe %CMAKELISTS_DIR% -G %GENERATOR% %ARCH_OPTION% %VS_TOOLSET_OPTION% ^
+cmake.exe %CMAKELISTS_DIR% -G %GENERATOR% %ARCH_OPTION% ^
     -DCMAKE_INSTALL_PREFIX="%CMAKE_INSTALL_PREFIX%" ^
     -DWITH_ROCKSDB=On -DWITH_ZSTD=On ^
     -DCMAKE_PREFIX_PATH="%CMAKE_PREFIX_PATH%" ^

win/vs-cfg.cmd

@@ -171,24 +171,15 @@ IF %VS_VER%==2026 ( set "VC_VER=14.5" )
 set BOOST_BOOTSTRAP_VER=vc%VC_VER%
 set BOOST_BOOTSTRAP_VER=%BOOST_BOOTSTRAP_VER:.=%
 
-set VS_TOOLSET_HOST=
-
 :: determine the toolset and winapi for Boost b2
-:: optionally use 64bit toolset to work around memory errors when linking
 IF DEFINED VS_TOOLSET (
     set BOOST_TOOLSET=msvc-%BOOST_TOOLSET%
     if "!VS_TOOLSET:~-3!"=="_xp" (
         set BOOST_WIN_API=define=BOOST_USE_WINAPI_VERSION=0x0501
     )
-    IF NOT "%VS_HOST%"=="" (
-        set VS_TOOLSET_HOST=%VS_TOOLSET%,host=%VS_HOST%
-    )
 ) ELSE (
     set BOOST_TOOLSET=msvc-%VC_VER%
     set BOOST_WIN_API=
-    IF NOT "%VS_HOST%"=="" (
-        set VS_TOOLSET_HOST=host=%VS_HOST%
-    )
 )
 
 IF %VS_PLATFORM%==Win32 (