[MUMPS] Remove the injection of rpath_args through the inject_libs

variable. This should happen automatically through the Spack compiler
wrapper.

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

@@ -203,10 +203,7 @@ def write_makefile_inc(self):
 
         if '+shared' in self.spec:
             # All Mumps libraries will be linked with 'inject_libs'.
-            # Usually, the rpaths will be injected by the Spack compiler
-            # wrapper, however some MPI wrappers may not call the Spack
-            # compiler wrapper.
-            inject_libs = [self.rpath_args]
+            inject_libs = []
             if '+mpi' in self.spec:
                 inject_libs += [self.spec['scalapack'].libs.ld_flags]
             if '+ptscotch' in self.spec or '+scotch' in self.spec: