Basic template for using MPI with zig. Only tested with OpenMPI 5.0.5-2 for now, but likely works with other (recent) versions. Might expand to other implementations in future.

All steps for creating an mpi zig module are in build_mpi.zig, which:

• Finds the system MPI header
• Makes a temporary copy in the zig cache with the OMPI_PREDEFINED_GLOBAL macro definition and usage patched to be friendly to translate-c
• Sets up the translate-c build step
• Provides a helper function for linking MPI

Relies on being able to call mpicc --showme:arg to query include directories, library directories, and the MPI library name for linkage. Also checks link flags to extract rpath if possible, although this may not work if the base compiler is not gcc, and all other flags are currently ignored.