[clang] [llvm] [OpenMP] Remove 'libomptarget.devicertl.a' fatbinary and use static library (PR #126143)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

I figured that calling it `libomptarget` was fine because we already have `libomptarget-amdgpu.bc` so what's the big difference in `amdgcn-amd-amdhsa/libomptarget.a`. But I can change it.

https://github.com/llvm/llvm-project/pull/126143