Fix build of dng_sdk for macOS

On mac, long and long long are of the same size, but int64_t is specifically defined as a long long.

Bug: N/A
Change-Id: Ib25cec45621c4eefc703de5f5e43b16dc0a010a3
Test: on a mac, lunch sdk & m libdng_sdk
(cherry picked from commit 1e1c945266845332b99d04a375729eee99826e22)
Merged-In: Ib25cec45621c4eefc703de5f5e43b16dc0a010a3
diff --git a/source/dng_safe_arithmetic.h b/source/dng_safe_arithmetic.h
index 66c5ebf..268c918 100644
--- a/source/dng_safe_arithmetic.h
+++ b/source/dng_safe_arithmetic.h
@@ -113,7 +113,7 @@
 #if __has_builtin(__builtin_smull_overflow)
 inline std::int64_t SafeInt64MultByClang(std::int64_t arg1, std::int64_t arg2) {
   std::int64_t result;
-#if LONG_MAX == INT64_MAX
+#if (LONG_MAX == INT64_MAX) && !defined(__APPLE__)
   if (__builtin_smull_overflow(arg1, arg2, &result)) {
 #else
   if (__builtin_smulll_overflow(arg1, arg2, &result)) {