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

[via llvm-commits]

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@@ -323,7 +327,7 @@ for libomptarget_target in config.libomptarget_all_targets:
             "%clang-" + libomptarget_target + add_libraries(" -O3 %s -o %t")))
         config.substitutions.append(("%libomptarget-run-" + \
             libomptarget_target, \
-            "%t"))
+            "%pre_bin %t"))
         config.substitutions.append(("%libomptarget-run-fail-" + \
             libomptarget_target, \
             "%not --crash %t"))
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jprotze wrote:

```suggestion
            "%not --crash %pre_bin %t"))
```

```suggestion
            "%pre_bin %not --crash %t"))
```
pre_bin is also necessary here. It is not clear to me, whether not should be the prefix to the test application or mpiexec

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