add first bottles for apple silicon #69

	name: macOS CI

	on:
	push:
	branches: [ main ]
	pull_request:
	branches: [ main ]

	jobs:
	build:

	runs-on: macos-latest

	steps:
	- name: initial checkout
	uses: actions/checkout@v2

	- name: cache Homebrew cache
	uses: actions/cache@v2
	with:
	path: /Users/runner/Library/Caches/Homebrew
	key: ${{ runner.os }}-sbt-${{ hashFiles('*.rb') }}

	- name: brew update
	run: brew update
	- name: tap riscv
	run: brew tap riscv/riscv
	- name: install tools
	run: brew install riscv-tools
	- name: test
	run: brew test riscv-tools

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