spack find mpiexec for impi (#42284)

lib/spack/spack/build_systems/cached_cmake.py

@@ -199,6 +199,8 @@ def initconfig_mpi_entries(self):
                 mpiexec = "/usr/bin/srun"
             else:
                 mpiexec = os.path.join(spec["slurm"].prefix.bin, "srun")
+        elif hasattr(spec["mpi"].package, "mpiexec"):
+            mpiexec = spec["mpi"].package.mpiexec
         else:
             mpiexec = os.path.join(spec["mpi"].prefix.bin, "mpirun")
             if not os.path.exists(mpiexec):

var/spack/repos/builtin/packages/intel-oneapi-mpi/package.py

@@ -113,6 +113,10 @@ class IntelOneapiMpi(IntelOneApiLibraryPackage):
 
     provides("mpi@:3.1")
 
+    @property
+    def mpiexec(self):
+        return self.component_prefix.bin.mpiexec
+
     @property
     def v2_layout_versions(self):
         return "@2021.11:"