Resolve `make: *** No rule to make target `ggml-metal.m', needed by `…

[beebopkim]

Resolve make: *** No rule to make target `ggml-metal.m', needed by `ggml-metal.o'. Stop. on macOS Metal when executing LLAMA_METAL=1 make.

Tested on M1 Max and works well.

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[LostRuins]

Thanks!