objtool: Exit successfully when requesting help

When the user requests help it's not an error so do not exit with
a non-zero exit code. This is not especially useful for a user but
any script that might wish to check that objtool --help is at least
available can't rely on the exit code to crudely check that, for
example, building an objtool executable succeeds.
Signed-off-by: Matt Helsley <mhelsley@vmware.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

tools/objtool/objtool.c

@@ -58,7 +58,9 @@ static void cmd_usage(void)
 
 	printf("\n");
 
-	exit(129);
+	if (!help)
+		exit(129);
+	exit(0);
 }
 
 static void handle_options(int *argc, const char ***argv)