cros-unibuild: Add unibuild_install_touch_workdir

Add a version of unibuild_install_touch_files which pulls from $WORKDIR..
This is where CPFE files are placed using cros-binary_add_gs_uri.

BUG=b:175749947
TEST=Verify both unibuild_install_touch_files/workdir

Change-Id: Ia808a203dfcfa83c21fe97c3b24e8d9ee12325f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2594191
Tested-by: Bob Moragues <moragues@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: C Shapiro <shapiroc@chromium.org>
1 file changed