fix unknown pragma warning when building with non-clang

src/google/protobuf/wire_format_lite.cc

@@ -665,9 +665,11 @@ static size_t VarintSize(const T* data, const int n) {
     if (x > 0x1FFFFF) sum++;
     if (x > 0xFFFFFFF) sum++;
   }
+#ifdef __clang__
 // Clang is not smart enough to see that this loop doesn't run many times
 // NOLINTNEXTLINE(google3-runtime-pragma-loop-hint): b/315043579
 #pragma clang loop vectorize(disable) unroll(disable) interleave(disable)
+#endif
   for (; i < n; i++) {
     uint32_t x = data[i];
     if (ZigZag) {
@@ -707,9 +709,11 @@ static size_t VarintSize64(const T* data, const int n) {
     if (x > 0x1FFFFF) sum++;
     if (x > 0xFFFFFFF) sum++;
   }
+#ifdef __clang__
 // Clang is not smart enough to see that this loop doesn't run many times
 // NOLINTNEXTLINE(google3-runtime-pragma-loop-hint): b/315043579
 #pragma clang loop vectorize(disable) unroll(disable) interleave(disable)
+#endif
   for (; i < n; i++) {
     uint64_t x = data[i];
     if (ZigZag) {