Add missing mips64 lib-bootstrap

Such that the following can correctly populate sysroot just enough to rebuild
mips64el toolchain

  ./build/tools/gen-platforms.sh --minimal --dst-dir=$NDK --ndk-dir=$NDK --arch=mips64

Change-Id: Ib37516bfe4c4b6a0c5b479d7cec8764c161f02c8
11 files changed