This feature is necessary when the cross compilers need to be rebuilt
because the goroot has been updated but the ndk version has not changed, or
when rebuilding is required but there is no network.
Currently the test for usable ndk compilers is simply checking
the presence of a file that's created after the ndk tool chain is installed
in the $GOPATH/pkg/gomobile/androind-<ndkversion> directory.
The -u option forces update of the ndk tool chain regardless.
Change-Id: I3d4f62266d436ddc52d158877f08481f92a6a690
Reviewed-on: https://go-review.googlesource.com/5140
Reviewed-by: David Crawshaw <crawshaw@golang.org>
eada1f182c