Revert "[CMake] Ensure `CLANG_RESOURCE_DIR` is respected."

This reverts commit 39aa0f5c434b463520ac39a8dbe933ee8c4c5ea7.

This is missing the new GetClangResourceDir.cmake that is being included,
so all clang builds are broken.

GitOrigin-RevId: d072d110227d118284cb4484814567782ab50186
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1efcaf..04678cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -90,8 +90,8 @@
 if(${OPENMP_STANDALONE_BUILD})
   set(LIBOMP_HEADERS_INSTALL_PATH "${CMAKE_INSTALL_INCLUDEDIR}")
 else()
-  include(GetClangResourceDir)
-  get_clang_resource_dir(LIBOMP_HEADERS_INSTALL_PATH SUBDIR include)
+  string(REGEX MATCH "[0-9]+" CLANG_VERSION ${PACKAGE_VERSION})
+  set(LIBOMP_HEADERS_INSTALL_PATH "${OPENMP_INSTALL_LIBDIR}/clang/${CLANG_VERSION}/include")
 endif()
 
 # Build host runtime library, after LIBOMPTARGET variables are set since they are needed