Reminder: simplify metal bytecode compilation pipeline...

[floooh]

Apparently calling the separate metallib tool isn't needed anymore:

https://twitter.com/SebAaltonen/status/1844661256252194911

...but it would only make sense if we could get rid of the temporary .air and .dia files. Maybe calling metal with multiple input files works too?

[floooh]

PS: also:

You still need to call metal twice. Once for compiling, once for .metallib linking. Just replace metallib command with metal command and it works. It's undocumented, but it works and avoids the recent bug in metallib command.

Now that you are calling metal twice, you need also -frecord-sources in your linker call. This wasn't needed with metallib.