Support pgi + openmpi combination

mpcdf_common.py

@@ -120,12 +120,17 @@ def mpi_module(mpi_repo):
 
 
 def valid_pgi_mpi(pgi, mpi):
-    if "impi" not in mpi:
-        return False
+    if "impi" in mpi:
         if "2017" in mpi:
             return False
+        else:
+            return True
+
+    if "openmpi_4" == mpi:
         return True
 
+    return False
+
 
 def valid_mpi(compiler, mpi):
     """