Reland [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 e774b20a1fd74d8301bafae8c179caf4f89cf312..51d68cffe2a3fe771cf7b6ee69196f2419a4a95d 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -194,6 +194,12 @@ 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 ------------------------------------------------------------