Fix db_bench_tool_test (#7935)

Summary:
The patch fixes the build for `db_bench_tool_test` and makes the tests pass.
Namely, it fixes the following issues:

* https://github.com/facebook/rocksdb/issues/7703 removed the member variable `fs_` but the test case `OptionsFileMultiLevelUniversal`
was not updated.
* https://github.com/facebook/rocksdb/issues/7344 fixed the `OptionsFile` test case for the case when Snappy is *not* available but at the
same time broke it for the case when it *is* available. (The test used a default-constructed
`ColumnFamilyOptions` object, and the default value of the `compression` option is either
Snappy or no compression depending on whether Snappy is supported.)
* The test used `google::ParseCommandLineFlags` instead of
`GFLAGS_NAMESPACE::ParseCommandLineFlags`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7935

Test Plan: Ran the test both with and without Snappy support.

Reviewed By: zhichao-cao

Differential Revision: D26269765

Pulled By: ltamasi

fbshipit-source-id: b7303d8a981ab299d22ab540e0cbd12d149ed9bb

tools/db_bench_tool_test.cc

@@ -127,7 +127,7 @@ TEST_F(DBBenchTest, OptionsFile) {
   const std::string kOptionsFileName = test_path_ + "/OPTIONS_test";
   Options opt = GetDefaultOptions();
   ASSERT_OK(PersistRocksDBOptions(DBOptions(opt), {"default"},
-                                  {ColumnFamilyOptions()}, kOptionsFileName,
+                                  {ColumnFamilyOptions(opt)}, kOptionsFileName,
                                   opt.env->GetFileSystem().get()));
 
   // override the following options as db_bench will not take these
@@ -164,7 +164,7 @@ TEST_F(DBBenchTest, OptionsFileMultiLevelUniversal) {
 
   ASSERT_OK(PersistRocksDBOptions(DBOptions(opt), {"default"},
                                   {ColumnFamilyOptions(opt)}, kOptionsFileName,
-                                  fs_.get()));
+                                  opt.env->GetFileSystem().get()));
 
   // override the following options as db_bench will not take these
   // options from the options file
@@ -316,7 +316,7 @@ TEST_F(DBBenchTest, OptionsFileFromFile) {
 
 int main(int argc, char** argv) {
   ::testing::InitGoogleTest(&argc, argv);
-  google::ParseCommandLineFlags(&argc, &argv, true);
+  GFLAGS_NAMESPACE::ParseCommandLineFlags(&argc, &argv, true);
   return RUN_ALL_TESTS();
 }