Update AddSwift.cmake

Author: drexin

cmake/modules/AddSwift.cmake

@@ -350,8 +350,10 @@ function(_add_variant_c_compile_flags)
   endif()
 
   if("${CFLAGS_SDK}" STREQUAL "LINUX")
-    # this is the minimum architecture that supports 16 byte CAS, which is necessary to avoid a dependency to libatomic
-    list(APPEND result "-march=core2")
+    if(${CFLAGS_ARCH} STREQUAL x86_64)
+      # this is the minimum architecture that supports 16 byte CAS, which is necessary to avoid a dependency to libatomic
+      list(APPEND result "-march=core2")
+    endif()
   endif()
 
   set("${CFLAGS_RESULT_VAR_NAME}" "${result}" PARENT_SCOPE)