build_image: mask out /build/bin from images

We don't want these installed into the rootfs.

BUG=None
TEST=CQ passes

Change-Id: I2251bf9714cacaf22046ee844524d57a4dd30b98
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3754481
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Dan Callaghan <dcallagh@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/common.sh b/common.sh
index c368a20..77abc60 100644
--- a/common.sh
+++ b/common.sh
@@ -345,6 +345,7 @@
   *.hxx
   *.proto
   */.keep*
+  /build/bin
   /build/initramfs
   /build/libexec/tast
   /build/manatee