CMake: Add support for building with OpenMP support for clang on windows.

mostly minor c/cxx/linker flags, only tested with clang 9.0.0

Differential Revision: https://developer.blender.org/D5976

Reviewers: brecht, jesterking

source/creator/CMakeLists.txt

@@ -674,6 +674,13 @@ elseif(WIN32)
 
   set(BLENDER_TEXT_FILES_DESTINATION ".")
 
+  if(WITH_OPENMP AND MSVC_CLANG)
+    install(
+          FILES ${CLANG_OPENMP_DLL}
+          DESTINATION "."
+    )
+  endif()
+
   if(WITH_PYTHON)
     string(REPLACE "." "" _PYTHON_VERSION_NO_DOTS ${PYTHON_VERSION})