[Darwin] Disable NSAsserts in release builds. (#860)

Chromium has a similar gn flag to disable asserts in release builds: https://source.chromium.org/chromium/chromium/src/+/main:build/config/BUILD.gn;drc=9dab28144192cefadbb96b778ef866ea3deb74ff;l=148

Related: flutter/flutter#148279

Author: bc-lee

build/config/BUILD.gn

@@ -84,6 +84,11 @@ config("debug") {
 config("release") {
   defines = [ "NDEBUG" ]
 
+  if (is_mac || is_ios) {
+    # Disable NSAsserts in release builds.
+    defines += [ "NS_BLOCK_ASSERTIONS=1" ]
+  }
+
   # Sanitizers.
   # TODO(GYP) The GYP build has "release_valgrind_build == 0" for this
   # condition. When Valgrind is set up, we need to do the same here.