One full round of make.bash is saved with this change.

Change-Id: I8ad1442e9e1255b9abe14dbfec4c903d897d6015
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/7976Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>