modify compile warning

Signed-off-by: lifansheng <lifansheng1@huawei.com>

BUILD.gn

@@ -221,7 +221,7 @@ config("ark_jsruntime_config") {
 config("ecma_test_config") {
   visibility = [ ":*" ]
 
-  cflags_cc = [ "-Wno-sign-compare" ]
+  cflags_cc = []
 }
 
 ecma_source = [

run_test262.sh

@@ -15,7 +15,7 @@
 set -e
 
 pushd ark/ts2abc
-    time=`date +'%Y%m%d%H%M%S'`
+    time=$(date +'%Y%m%d%H%M%S')
     if [ ! -d report ];then
         mkdir report
     fi
@@ -35,7 +35,7 @@ pushd ark/ts2abc
     cp out/test262/result.txt report/result_es2015_${time}.txt
 
     pushd report
-        es2015_fail=`grep FAIL result_es2015_${time}.txt | wc -l`
+        es2015_fail=$(grep FAIL result_es2015_${time}.txt | wc -l)
         threshold=0
         if [ ${es2015_fail} -gt ${threshold} ];then
             echo 'test262 fail case over thresgold'