Support pgi + openmpi combination

mpcdf_common.py

@@ -120,11 +120,16 @@ def mpi_module(mpi_repo):
 
 
 def valid_pgi_mpi(pgi, mpi):
-    if "impi" not in mpi:
-        return False
-    if "2017" in mpi:
-        return False
-    return True
+    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):