build: simplify clean.bash

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4257045

src/clean.bash

@@ -22,11 +22,6 @@ rm -f "$GOROOT"/lib/*.a
 for i in lib9 libbio libmach cmd pkg \
 	../misc/cgo/gmp ../misc/cgo/stdio \
 	../test/bench ../test/garbage
-do(
-	cd "$GOROOT"/src/$i || exit 1
-	if test -f clean.bash; then
-		bash clean.bash --gomake $MAKE
-	else
-		$MAKE clean
-	fi
-)done
+do
+	gomake -C "$GOROOT/src/$i" clean
+done

test/bench/Makefile

@@ -0,0 +1,14 @@
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../src/Make.inc
+
+all:
+	@echo "make clean or timing"
+
+timing:
+	./timing.sh
+
+clean:
+	rm -f [568].out *.[568]

test/bench/clean.bash

@@ -1,4 +0,0 @@
-#!/bin/sh
-
-OS=568
-rm -f [$OS].out *.[$OS]