enable three warning on LLVMSupport

Signed-off-by: Zhu, Shaojie <[email protected]>

Author: ShaojieZhuIntel

llvm/lib/Support/CMakeLists.txt

@@ -291,17 +291,13 @@ add_llvm_component_library(LLVMSupport
   LINK_COMPONENTS
   Demangle
   )
-
-if(BUILD_COMPILER_FOR_DRIVER)
-  get_target_property(CURRENT_COMPILE_OPTIONS LLVMSupport COMPILE_OPTIONS)
-  message(STATUS "Current compile options: ${CURRENT_COMPILE_OPTIONS}")
-  string(REPLACE "/wd4146" "" NEW_COMPILE_OPTIONS "${CURRENT_COMPILE_OPTIONS}")
-  string(REPLACE "/wd4244" "" NEW_COMPILE_OPTIONS "${NEW_COMPILE_OPTIONS}")
-  string(REPLACE "/wd4267" "" NEW_COMPILE_OPTIONS "${NEW_COMPILE_OPTIONS}")
-  string(REPLACE ";;" ";" NEW_COMPILE_OPTIONS "${NEW_COMPILE_OPTIONS}")
-  set_target_properties(LLVMSupport PROPERTIES COMPILE_OPTIONS "${NEW_COMPILE_OPTIONS}")
-  get_target_property(NEW_COMPILE_OPTIONS LLVMSupport COMPILE_OPTIONS)
-  message(STATUS "New compile options: ${NEW_COMPILE_OPTIONS}")
+  
+if(MSVC)
+  if(BUILD_COMPILER_FOR_DRIVER)
+    target_compile_options(LLVMSupport PRIVATE
+      /w34146 /w34244 /w34267
+    )
+  endif()
 endif()
 
 set(llvm_system_libs ${system_libs})