[clang] [clang][AMDGPU] Enable module splitting by default (PR #128509)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

I'm thinking this should be default only for HIP (maybe OpenMP later) because the option is HIP only and it confounds attempts to override it by inserting a linker option otherwise.

https://github.com/llvm/llvm-project/pull/128509