[libFuzzer][MSVC] Make attribute-use compatible with MSVC

Summary:
Replace attributes with macros that use equivalent declspecs
for MSVC.

Reviewers: vitalybuka

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D56512

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@351456 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerValueBitMap.h b/FuzzerValueBitMap.h
index 13d7cbd..a7c24f8 100644
--- a/FuzzerValueBitMap.h
+++ b/FuzzerValueBitMap.h
@@ -65,7 +65,7 @@
   }
 
  private:
-  uintptr_t Map[kMapSizeInWords] __attribute__((aligned(512)));
+  ATTRIBUTE_ALIGNED(512) uintptr_t Map[kMapSizeInWords];
 };
 
 }  // namespace fuzzer