petsc: fix scalapack error: (#4341)

Specify either "--with-scalapack-dir" or "--with-scalapack-lib --with-scalapack-include". But not both!

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

@@ -198,7 +198,7 @@ def install(self, spec, prefix):
 
         # Activates library support if needed
         for library in ('metis', 'boost', 'hdf5', 'hypre', 'parmetis',
-                        'mumps', 'scalapack', 'trilinos'):
+                        'mumps', 'trilinos'):
             options.append(
                 '--with-{library}={value}'.format(
                     library=library, value=('1' if library in spec else '0'))