Fix dawn.cmake for macos

Author: junjihashimoto

cmake/dawn.cmake

@@ -111,8 +111,6 @@ if(NOT DAWN_BUILD_FOUND)
     SUBBUILD_DIR ${DAWN_BUILD_DIR}/tmp
     BINARY_DIR   ${DAWN_BUILD_DIR}
   )
-  FetchContent_MakeAvailable(dawn)
-
   # Remove -msse4.1 flag from abseil-cpp after fetching Dawn
   if(APPLE)
     set(ABSEIL_COPTS_FILE "${DAWN_DIR}/third_party/abseil-cpp/absl/copts/GENERATED_AbseilCopts.cmake")
@@ -124,6 +122,8 @@ if(NOT DAWN_BUILD_FOUND)
     endif()
   endif()
 
+  FetchContent_MakeAvailable(dawn)
+
   set(CMAKE_INCLUDE_PATH "${CMAKE_INCLUDE_PATH};${DAWN_DIR}/src" CACHE INTERNAL "")
 
   set(DAWN_BUILD_FOUND ON)