drop references to /usr/local/portage symlinks

Now that all code uses the overlays directly, we don't need these
anymore, so stop creating them.

BUG=b:191307774
TEST=CQ passes

Change-Id: I97e07cc1aa2e853d978ba4c642a3693b96852622
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3633060
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Commit-Queue: Sergey Frolov <sfrolov@google.com>
1 file changed