sdk declaration should accept ".a" files

[smackie]

The current validation check for sdk definitions to be either .framework or .tbd is a little too tight. It would be useful to also accept .a as an extension and to treat them as-is (i.e. no additional path specification). This allows the library search path to be specified in the central xcconfig and the library name to be used in the project (rather than always having to specify the full path with a leading "/").

I'd be happy to contribute a patch for this if it sounds acceptable. Cheers!

[yonaskolb]

Hi @smackie, the intent sounds good. Not totally clear on the details, but would happily look over a PR 👍

[smackie]

Hi @yonaskolb, I had a look at a patch earlier which I'll organize for a review in a day or two. Thanks for this tool - it's an absolute blessing. Cheers!