Fix a minor regression script issue (facebook#8755)

Summary:
The system default `time` doesn't support option -v

Pull Request resolved: facebook#8755

Test Plan: CI: https://www.internalfb.com/intern/sandcastle/job/13510799359724405

Reviewed By: ltamasi

Differential Revision: D30757119

Pulled By: jay-zhuang

fbshipit-source-id: 093e5084f3b7cc71f6795b1062f48d4e77ed4518

build_tools/rocksdb-lego-determinator

@@ -1103,7 +1103,7 @@ NO_COMPRESSION_COMMANDS="[
 #
 run_regression()
 {
-  time -v bash -vx ./build_tools/regression_build_test.sh $(mktemp -d  $WORKING_DIR/rocksdb.XXXX) $(mktemp rocksdb_test_stats.XXXX)
+  time bash -vx ./build_tools/regression_build_test.sh $(mktemp -d  $WORKING_DIR/rocksdb.XXXX) $(mktemp rocksdb_test_stats.XXXX)
 
   # ======= report size to ODS ========
 
@@ -1344,7 +1344,7 @@ case $1 in
   run_regression)
     set -e
     run_regression
-    unset -e
+    set +e
     ;;
   java_build)
     echo $JAVA_BUILD_TEST_COMMANDS