Fix Appveyor build due to signed/unsigned comparison

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/5788

Test Plan: Travis CI and Appveyor should complete successfully.

Differential Revision: D17287422

Pulled By: anand1976

fbshipit-source-id: d9408b692f78be95d0088b29b33f6a8ff40ec97b

db/plain_table_db_test.cc

@@ -773,12 +773,12 @@ TEST_P(PlainTableDBTest, BloomSchema) {
       uint32_t pattern;
       if (!bloom_locality) {
         pattern = 1785868347UL;
-      } else if (CACHE_LINE_SIZE == 64) {
+      } else if (CACHE_LINE_SIZE == 64U) {
         pattern = 2421694657UL;
-      } else if (CACHE_LINE_SIZE == 128) {
+      } else if (CACHE_LINE_SIZE == 128U) {
         pattern = 788710956UL;
       } else {
-        ASSERT_EQ(CACHE_LINE_SIZE, 256);
+        ASSERT_EQ(CACHE_LINE_SIZE, 256U);
         pattern = 163905UL;
       }
       bool expect_fp = pattern & (1UL << i);