Don't overwrite user's args

If the cmd provided to spawn doesn't match
argv0, then assume that the user may have put the argv
for their cmd in the argv array, but not
started with the actual cmd - so add it
to the front of the array

Signed-off-by: Ralph Castain <rhc@pmix.org>

src/client/pmix_client_spawn.c

@@ -239,8 +239,11 @@ PMIX_EXPORT pmix_status_t PMIx_Spawn_nb(const pmix_info_t job_info[], size_t nin
             tmp = pmix_basename(aptr->cmd);
             t2 = pmix_basename(aptr->argv[0]);
             if (0 != strcmp(tmp, t2)) {
-                free(appsptr[n].argv[0]);
-                appsptr[n].argv[0] = strdup(tmp);
+                // assume that the user may have put the argv
+                // for their cmd in the argv array, but not
+                // started with the actual cmd - so add it
+                // to the front of the array
+                PMIx_Argv_prepend_nosize(&appsptr[n].argv, tmp);
             }
             free(tmp);
             free(t2);