[clang] [Modules] Add -cc1 -flate-module-map-file to load module maps after PCMs (PR #88893)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 commented:

(I just missed it initially.)

I took a quick look and the change looks at least not bad to me.

But I didn't have experience with clang modules and I don't have an idea for the concerns you list.

I don't mind accepting this if you want to land this. I feel it won't affect users. But let's give some time for discussing.

https://github.com/llvm/llvm-project/pull/88893