Support or test case for .metal files

[thiagohmcruz]

See bazelbuild/rules_apple#725

I was asked if we support that in rules_ios but I'd have to dig a bit to fully answer that question. It is supported in rules_apple so in theory we can consume that.

Using this issue to track the work to add support for .metal files if there's anything rules_ios specific we need to do (including adding test cases and examples).

[mattrobmattrob]

We are currently using .metal files stored in a precompiled_apple_resource_bundle with rules_ios. Not sure apple_framework data/resource attributes handle it through. 👍

[thiagohmcruz]

Cool, thx for sharing. We just hit issues when pulling that type of file from a Pod, so there's the BUILD file translation problem (not on rules_ios to handle that) and the "rules that need to be used and how" problem.

At a minimum I think this issue should be resolved once we have at least a few test cases/examples checked-in for folks to reference.