Finally, this patch moves from round-tripping one `CompilerInvocation` at a time to round-tripping the invocation as a whole.
This patch includes only the code required to make round-tripping the whole invocation work. More cleanups will be done in a follow-up patch.
Depends on D96847, D97041 & D97042.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D96280
This patch implements generation of remaining header search arguments.
It's done manually in C++ as opposed to TableGen, because we need the flexibility and don't anticipate reuse.
This patch also tests the generation of header search options via a round-trip. This way, the code gets exercised whenever Clang is built and tested in asserts mode. All `check-clang` tests pass.
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D94472
Jan Svoboda