make.bat: incease runtime test timeout to 300s (fixes build)
make.bat: incease runtime test timeout to 300s (fixes build)

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/11064044

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang