Fix DBTest.DynamicMiscOptions so it passes even with Snappy disabled (#5438)

Summary:
This affects our "no compression" automated tests. Since PR #5368, DBTest.DynamicMiscOptions has been failing with:

db/db_test.cc:4889: Failure
dbfull()->SetOptions({{"compression", "kSnappyCompression"}})
Invalid argument: Compression type Snappy is not linked with the binary.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5438

Differential Revision: D15752100

Pulled By: ltamasi

fbshipit-source-id: 3f19eff7cafc03b333965be0203c5853d2a9cb71

db/db_test.cc

@@ -4884,14 +4884,15 @@ TEST_F(DBTest, DynamicMiscOptions) {
   ASSERT_OK(dbfull()->TEST_GetLatestMutableCFOptions(handles_[0],
                                                      &mutable_cf_options));
   ASSERT_EQ(CompressionType::kNoCompression, mutable_cf_options.compression);
-  // Appveyor fails with: Compression type Snappy is not linked with the binary
-#ifndef OS_WIN
-  ASSERT_OK(dbfull()->SetOptions({{"compression", "kSnappyCompression"}}));
-  ASSERT_OK(dbfull()->TEST_GetLatestMutableCFOptions(handles_[0],
-                                                     &mutable_cf_options));
-  ASSERT_EQ(CompressionType::kSnappyCompression,
-            mutable_cf_options.compression);
-#endif
+
+  if (Snappy_Supported()) {
+    ASSERT_OK(dbfull()->SetOptions({{"compression", "kSnappyCompression"}}));
+    ASSERT_OK(dbfull()->TEST_GetLatestMutableCFOptions(handles_[0],
+                                                       &mutable_cf_options));
+    ASSERT_EQ(CompressionType::kSnappyCompression,
+              mutable_cf_options.compression);
+  }
+
   // Test paranoid_file_checks already done in db_block_cache_test
   ASSERT_OK(
       dbfull()->SetOptions(handles_[1], {{"paranoid_file_checks", "true"}}));