Implement correct OS and CC detection.

src/misc-intrinsics.h

Index: src/misc-intrinsics.h
diff --git a/src/misc-intrinsics.h b/src/misc-intrinsics.h
index 5393de2c2175963a3f978eecbfd91189d869f975..35a243435c31f3f1d317a6859aded538e17274ec 100644
--- a/src/misc-intrinsics.h
+++ b/src/misc-intrinsics.h
@@ -39,13 +39,13 @@ namespace internal {
 // Result is undefined if input is zero.
 int IntegerLog2(uint32_t value);
 
-#if defined(__GNUC__)
+#if V8_CC_GNU
 
 inline int IntegerLog2(uint32_t value) {
   return 31 - __builtin_clz(value);
 }
 
-#elif defined(_MSC_VER)
+#elif V8_CC_MSVC
 
 #pragma intrinsic(_BitScanReverse)