Fabric build output should be compatible with Fabric distribution system

[boundsj]

I'm finding that the last iOS release that appears to be compatible with Fabric is ios-v3.2.3. In ios-v3.3.0-alpha.1 we migrated iOS and macOS targets to checked in Xcode projects. Some part of this change appears to have broken the way an app using the Mapbox SDK via Fabric pulls in Objective-C categories. This results in a runtime error:

[NSProcessInfo mgl_isInterfaceBuilderDesignablesAgent]: unrecognized selector sent to instance ...

Digging a bit deeper, ios-v3.3.0-alpha.1 actually broke projects that use the static framework entirely. So, if you used 3.3.0-alpha.1 to 3.3.0-alpha.3 you could not even build an app using the Fabric project template.

In ios-v3.3.0-beta.1 we fixed an issue where applications could not link to the Mapbox library as a static lib. However, it appears that more changes are probably required to regain compatibility with Fabric.

cc @friedbunny @1ec5 @incanus

[1ec5]

Probably related to 7a38e56. We should verify the statement in that commit message that -ObjC in the static framework build target is sufficient for getting the SDK’s category methods into the final built binary.

[boundsj]

@1ec5 @incanus adding -ObjC to the Fabric generated project allows an app made with the project to run fine using the latest Fabric build output from master. I get the sense from looking at the add/remove -ObjC flag oscillations over the last year that we should probably go ahead and revert 7a38e56, unfortunately, just for Fabric. Ok?

[1ec5]

We'd have to add a whole lot more of the C function hack because we have a lot more categories than we used to.

[boundsj]

Closing ref #8969