meta-google: gbmc-bridge: Fix do_rm_work

The workdir will be empty if the package is populated from the sstate,
fix the command to work for this case.

Change-Id: Ie262a69de067e94e9da32ca8a89d1db1a5ab5bf2
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-google/recipes-google/networking/gbmc-bridge.bb b/meta-google/recipes-google/networking/gbmc-bridge.bb
index bacb349..37af84b 100644
--- a/meta-google/recipes-google/networking/gbmc-bridge.bb
+++ b/meta-google/recipes-google/networking/gbmc-bridge.bb
@@ -101,6 +101,5 @@
 do_rm_work_prepend() {
   # HACK: Work around broken do_rm_work not properly calling rm with `--`
   # It doesn't like filenames that start with `-`
-  mkdir -p ${WORKDIR}/done
-  mv -- ${WORKDIR}/-* ${WORKDIR}/done
+  rm -rf -- ${WORKDIR}/-*
 }