test/64bit.go:  segfaults on sheevaplug(armv5)

The following have long runtimes when GC is on.
Sample run time in seconds for android emulator
and sheevaplug
test/stack.go:          4934s   1780s
test/ken/chan.go:        860s    296s
test/gc1.go:             218s     69s

R=rsc, kaib
CC=golang-dev
https://golang.org/cl/749041