Remove ReadOnly part of PinnableSliceAndMmapReads from Lite (#4070)

Summary:
Lite does not support readonly DBs.
Closes https://github.com/facebook/rocksdb/pull/4070

Differential Revision: D8677858

Pulled By: maysamyabandeh

fbshipit-source-id: 536887d2363ee2f5d8e1ea9f1a511e643a1707fa

db/db_test2.cc

@@ -2526,10 +2526,11 @@ TEST_F(DBTest2, PinnableSliceAndMmapReads) {
   // compaction. It crashes if it does.
   ASSERT_EQ(pinned_value.ToString(), "bar");
 
+#ifndef ROCKSDB_LITE
   pinned_value.Reset();
   // Unsafe to pin mmap files when they could be kicked out of table cache
   Close();
-  ReadOnlyReopen(options);
+  ASSERT_OK(ReadOnlyReopen(options));
   ASSERT_EQ(Get("foo", &pinned_value), Status::OK());
   ASSERT_FALSE(pinned_value.IsPinned());
   ASSERT_EQ(pinned_value.ToString(), "bar");
@@ -2539,10 +2540,11 @@ TEST_F(DBTest2, PinnableSliceAndMmapReads) {
   // value and avoid the memcpy
   Close();
   options.max_open_files = -1;
-  ReadOnlyReopen(options);
+  ASSERT_OK(ReadOnlyReopen(options));
   ASSERT_EQ(Get("foo", &pinned_value), Status::OK());
   ASSERT_TRUE(pinned_value.IsPinned());
   ASSERT_EQ(pinned_value.ToString(), "bar");
+#endif
 }
 
 }  // namespace rocksdb