Add strip_prefix_header to objc_library rule

[ob]

I'm trying to add an external dependency (OCHamcrest) which has all of its includes as:

#include <OCHamcrest/Foo.h>

I was trying to remove the OCHamcrest prefix in my objc_library rule, but found it has no support for it. Is there another way of stripping the prefix without having to modify all files?

[thomasvl]

objc_library is currently a native rule in bazel, so you'll want to open this against bazel.

At some point in the future we may look at moving objc_library to skylark and bundling it here, but that isn't current something that I think anyone is looking at.

[ob]

After doing some digging, I think bazelbuild/bazel#3712 is a better way. Closing this.