go : fixed Makefile for MacOS ARM 64 (#1530)
* Fixed Makefile for MacOS ARM 64 based on https://github.com/ggerganov/whisper.cpp/issues/1344 + proper ggml-metal env var setting
* conditional to fix broken non-macos compilation
* spaces -> tab
* make : fix whitespaces
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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
