runtime: fix TestGcLastTime on windows Intended to fix: http://build.golang.org/log/d6718ea67541b8c6be2bb14bcbc4e1c4261f67d7
runtime: fix TestGcLastTime on windows
Intended to fix:
http://build.golang.org/log/d6718ea67541b8c6be2bb14bcbc4e1c4261f67d7

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews
https://codereview.appspot.com/127520043

firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old