Add --ignore_unsupported_sandboxing to the bootstrap build

The recent change in the bootstrap process was causing a warning
about sandboxing not being activated.

--
MOS_MIGRATED_REVID=114106185
diff --git a/scripts/bootstrap/compile.sh b/scripts/bootstrap/compile.sh
index ee2481a..f9e6d31 100755
--- a/scripts/bootstrap/compile.sh
+++ b/scripts/bootstrap/compile.sh
@@ -227,6 +227,7 @@
       --workspace_directory=${PWD} \
       --nodeep_execroot --nofatal_event_bus_exceptions \
       build \
+      --ignore_unsupported_sandboxing \
       --startup_time=329 --extract_data_time=523 \
       --rc_source=/dev/null --isatty=1 --terminal_columns=97 \
       --ignore_client_env \