[OpenMP] Add CMake option to disable libarcher support

The support for `libarcher` can sometimes cause problems when running
tests or building. We want an option to turn this off when we are not
directly testing `libarcher`.

Reviewed By: jplehr

Differential Revision: https://reviews.llvm.org/D147343

openmp/tools/archer/CMakeLists.txt

@@ -6,9 +6,9 @@
 # //
 # //===----------------------------------------------------------------------===//
 
-  
+set(LIBOMP_ARCHER_SUPPORT TRUE CACHE BOOL "Build libomp with archer support")
 
-if(LIBOMP_OMPT_SUPPORT)
+if(LIBOMP_OMPT_SUPPORT AND LIBOMP_ARCHER_SUPPORT)
   include_directories(${LIBOMP_INCLUDE_DIR})
 
   add_library(archer SHARED ompt-tsan.cpp)