DBTest.DynamicLevelCompressionPerLevel should not run without snappy support

Summary: The test depends on snappy to be used. Skip the test if it is not supported.

Test Plan: Run the test

Reviewers: meyering, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D34995

db/db_test.cc

@@ -10666,6 +10666,9 @@ TEST(DBTest, DynamicLevelMaxBytesBase2) {
 }
 
 TEST(DBTest, DynamicLevelCompressionPerLevel) {
+  if (!SnappyCompressionSupported()) {
+    return;
+  }
   const int kNKeys = 120;
   int keys[kNKeys];
   for (int i = 0; i < kNKeys; i++) {