Add supports_two_phase_compilation to cxx toolchain

Summary:
allow-large-files

This opts into C++20 modules for specific toolchains we know work (onto which we cherry pick our upstream changes).

Reviewed By: apolloww, dmpolukhin

Differential Revision: D62382664

fbshipit-source-id: ff7fef8abe8a194387f257a2cbc4dd84fdc7195f

prelude/cxx/cxx_toolchain_types.bzl

@@ -123,6 +123,7 @@ _compiler_fields = [
     "preprocessor_flags",
     # Controls cache upload for object files
     "allow_cache_upload",
+    "supports_two_phase_compilation",
 ]
 
 HipCompilerInfo = provider(fields = _compiler_fields)