Force two rounds for the deterministic tests when no BAZEL_SUM is pro…

…vided

This resulted in most of the time on doing only one compilation and comparing
with the previous checksum of generally a older build, making the deterministic
test fails weirdly.

--
MOS_MIGRATED_REVID=96769326

compile.sh

@@ -132,8 +132,8 @@ fi
 #
 if [ $DO_CHECKSUM ]; then
   new_step "Determinism test"
-  BAZEL_SUM=${BAZEL_SUM:-bazel-out/bazel_checksum}
-  if [ ! -f ${BAZEL_SUM} ]; then
+  if [ ! -f ${BAZEL_SUM:-x} ]; then
+    BAZEL_SUM=bazel-out/bazel_checksum
     log "First build"
     bootstrap_test ${BAZEL} ${BAZEL_SUM}
   else