[clang] [clang][modules-driver] Precompile std modules independently of -o and final phase (PR #199289)

[Naveen Seth Hanig via cfe-commits]

naveen-seth wrote:

This should make -fmodules-driver compatible with godbolt, such that one can use `import std` and see the corresponding llvm ir or assembly (previously, only the execution view worked).

https://github.com/llvm/llvm-project/pull/199289