[llvm] [Offload] Add MPI Proxy Plugin (PR #114574)

[via llvm-commits]

================
@@ -194,8 +194,10 @@ set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} powerpc64-ibm-linux-g
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} powerpc64-ibm-linux-gnu-LTO")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} x86_64-unknown-linux-gnu")
 set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} x86_64-unknown-linux-gnu-LTO")
+set (LIBOMPTARGET_ALL_TARGETS "${LIBOMPTARGET_ALL_TARGETS} x86_64-unknown-linux-gnu-mpi")
----------------
jprotze wrote:

My understanding is that `x86_64-unknown-linux-gnu-mpi` offloads to remote hosts, while `nvptx64-nvidia-cuda-mpi` offloads to local/remote GPUs. No?
For compilation, the lit config drops the suffix just like the `-LTO` and `-JIT-LTO` suffix, which are also not part of the compiler target triple. @jhuber6 from my perspective the notion just follows current practice of defining test suites.

https://github.com/llvm/llvm-project/pull/114574