fix static mumps build error - Added a space at the end of ar vr for the static build to run successfully (#15407)

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

@@ -241,7 +241,7 @@ def write_makefile_inc(self):
         else:
             makefile_conf.extend([
                 'LIBEXT  = .a',
-                'AR = ar vr',
+                'AR = ar vr ',
                 'RANLIB = ranlib'
             ])