Let Bazel use sandboxing during bootstrap, if it's available.

--
MOS_MIGRATED_REVID=130406085
diff --git a/scripts/bootstrap/bootstrap.sh b/scripts/bootstrap/bootstrap.sh
index ab09cdb..14161ce 100755
--- a/scripts/bootstrap/bootstrap.sh
+++ b/scripts/bootstrap/bootstrap.sh
@@ -33,14 +33,12 @@
 if [ "${JAVA_VERSION}" = "1.7" ]; then
   : ${BAZEL_ARGS:=--java_toolchain=//src/java_tools/buildjar:bootstrap_toolchain_jdk7 \
         --host_java_toolchain=//src/java_tools/buildjar:bootstrap_toolchain_jdk7 \
-        --define JAVA_VERSION=1.7 \
-        --genrule_strategy=standalone --spawn_strategy=standalone \
+        --define JAVA_VERSION=1.7 --ignore_unsupported_sandboxing \
         "${EXTRA_BAZEL_ARGS:-}"}
 else
   : ${BAZEL_ARGS:=--java_toolchain=//src/java_tools/buildjar:bootstrap_toolchain \
         --host_java_toolchain=//src/java_tools/buildjar:bootstrap_toolchain \
-        --strategy=Javac=worker --worker_quit_after_build \
-        --genrule_strategy=standalone --spawn_strategy=standalone \
+        --strategy=Javac=worker --worker_quit_after_build --ignore_unsupported_sandboxing \
         "${EXTRA_BAZEL_ARGS:-}"}
 fi