update Makefile to use a LIBDIR variable to locate the preload library

This allows the ebuild will to supply the correct LIBDIR instead of
just assuming /lib in order to properly support multilib systems
This also requires the ebuild to pass LIBDIR to emake before it
becomes useful.

BUG=chromium-os:21805
TEST=build for x86-generic and amd64-generic and ensure minijail
works on both without problems loading libminijailpreload.so

Change-Id: I99a694ef37ba833a7e7c3850278d7f1d1c0b09ad
Reviewed-on: https://gerrit.chromium.org/gerrit/10680
Tested-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Elly Jones <ellyjones@chromium.org>
Commit-Ready: Sonny Rao <sonnyrao@chromium.org>
1 file changed