Merge pull request #1989 from KineticTheory/cray_compile_wrappers

On Cray machines, use the Cray compile wrappers instead of MPI wrappers.

var/spack/repos/builtin/packages/mpich/package.py

@@ -63,10 +63,18 @@ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.set('MPICH_FC', spack_fc)
 
     def setup_dependent_package(self, module, dep_spec):
-        self.spec.mpicc = join_path(self.prefix.bin, 'mpicc')
-        self.spec.mpicxx = join_path(self.prefix.bin, 'mpic++')
-        self.spec.mpifc = join_path(self.prefix.bin, 'mpif90')
-        self.spec.mpif77 = join_path(self.prefix.bin, 'mpif77')
+        # Is this a Cray machine? (TODO: We need a better test than this.)
+        if os.environ.get('CRAYPE_VERSION'):
+            self.spec.mpicc = spack_cc
+            self.spec.mpicxx = spack_cxx
+            self.spec.mpifc = spack_fc
+            self.spec.mpif77 = spack_f77
+        else:
+            self.spec.mpicc = join_path(self.prefix.bin, 'mpicc')
+            self.spec.mpicxx = join_path(self.prefix.bin, 'mpic++')
+            self.spec.mpifc = join_path(self.prefix.bin, 'mpif90')
+            self.spec.mpif77 = join_path(self.prefix.bin, 'mpif77')
+
         self.spec.mpicxx_shared_libs = [
             join_path(self.prefix.lib, 'libmpicxx.{0}'.format(dso_suffix)),
             join_path(self.prefix.lib, 'libmpi.{0}'.format(dso_suffix))