[clang][cli] Round-trip cc1 arguments in assert builds

This patch enables cc1 argument round-trip for assert builds. It can be disabled by building clang with `-DCLANG_ROUND_TRIP_CC1_ARGS=OFF`.

This will be committed only if we reach consensus in https://lists.llvm.org/pipermail/cfe-dev/2021-February/067714.html.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D97462