Build: Remove OpenMP

It's better for performance to use a single thread pool for all areas of
Blender, and this gets us closer to that.

Bullet, Quadriflow, Mantaflow and Ceres still contain OpenMP code, but it
was already disabled.

On macOS, our OpenMP libraries are no longer compatible with the latest
Xcode 16.3. By removing OpenMP we no longer have to solve that problem.

OpenMP was disabled for bpy module builds on Windows ARM64, which also no
longer needs to be solved.

Pull Request: https://projects.blender.org/blender/blender/pulls/136865

intern/opensubdiv/CMakeLists.txt

@@ -80,12 +80,6 @@ if(WITH_OPENSUBDIV)
     ${Epoxy_LIBRARIES}
   )
 
-  if(WITH_OPENMP AND WITH_OPENMP_STATIC)
-    list(APPEND LIB
-      ${OpenMP_LIBRARIES}
-    )
-  endif()
-
   if(WIN32)
     add_definitions(-DNOMINMAX)
     add_definitions(-D_USE_MATH_DEFINES)