Revert "Meta: Port recent changes to GN build"

This reverts commit 754ecc56dd33abef80a5fdf0550fa5a6311d8cc8.

This was handled by: 49b7539290238e92edca27a1d9a3eea89a11fa54.

Meta/gn/build/BUILD.gn

@@ -129,8 +129,6 @@ config("compiler_defaults") {
     ]
   }
 
-  cflags += [ "-Wno-invalid-offsetof" ]
-
   if (use_lld) {
     ldflags += [ "-fuse-ld=lld" ]
   }