Revert back to CMAKE_CXX_FLAGS override

Author: Pavel V Chupin

sycl/plugins/level_zero/CMakeLists.txt

@@ -16,23 +16,19 @@ if (NOT DEFINED LEVEL_ZERO_LIBRARY OR NOT DEFINED LEVEL_ZERO_INCLUDE_DIR)
     GIT_TAG           ${LEVEL_ZERO_LOADER_TAG}
   )
 
+  # Suppress some pedantic warnings for Level Zero build
+  set(CMAKE_CXX_FLAGS_BAK "${CMAKE_CXX_FLAGS}")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-but-set-variable")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-pedantic")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-stringop-truncation")
+
   FetchContent_MakeAvailable(level-zero-loader)
   FetchContent_GetProperties(level-zero-loader)
 
-  set(LEVEL_ZERO_LIBRARY ze_loader)
-
-  target_compile_options(${LEVEL_ZERO_LIBRARY} PRIVATE
-    "-Wno-unused-but-set-variable"
-    "-Wno-pedantic"
-    "-Wno-stringop-truncation"
-  )
-  target_compile_options(ze_tracing_layer PRIVATE
-    "-Wno-pedantic"
-  )
-  target_compile_options(ze_validation_layer PRIVATE
-    "-Wno-pedantic"
-  )
+  # Restore original flags
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS_BAK}")
 
+  set(LEVEL_ZERO_LIBRARY ze_loader)
   set(LEVEL_ZERO_INCLUDE_DIR
     ${level-zero-loader_SOURCE_DIR}/include CACHE PATH "Path to Level Zero Headers")
 endif()