sys-block/blktrace: Be sure rbtree is not compiled twice

Ensure all binaries are compiled on . before compiling other directory,
as btt/btt and blkiomon need the same file, rbtree.o.

See https://bugs.gentoo.org/705594

BUG=chromium:1035312
TEST=Confirm all binaries in . are compiled before btt/btt.

Change-Id: I654b61434433d81ffdc63ebda286de0977c2b7c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2005790
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
2 files changed