[iOS] Disable NSAssert and GTMDevAssert on release builds.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 80427f26a087b631031ad3a45bd017547898a4a9..09cb18f44434d3ded8b00e5911b57fa69b0196d0 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -221,6 +221,12 @@ config("release") {
       defines += [ "DYNAMIC_ANNOTATIONS_ENABLED=0" ]
     }
   }
+
+  if (is_ios) {
+    # Disable NSAssert and GTMDevAssert (from Google Toolbox for Mac). This
+    # follows XCode's default behavior for Release builds.
+    defines += [ "NS_BLOCK_ASSERTIONS=1" ]
+  }
 }
 
 # Default libraries ------------------------------------------------------------