build_packages: Only include sysroot packages in revdep consideration

Packages that aren't being installed to /build/$BOARD are BDEPEND
packages and should not be considered for the revdep logic.

BUG=chromium:1017840, chromium:1071530
TEST=`build_packages`

Change-Id: Icb759a5de2e9a66092f2d059c3984a262621a6ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2248406
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
1 file changed