Define a MSRV, use that toolchain by default. #10

	# This workflow verifies libtock-rs is usable on Mac OS.

	name: ci-mac-os

	# We run this workflow during pull request review, but not as a required status
	# for GitHub actions merge-queue merges. We can change this if the workflow is
	# reasonably quick and reliable.
	on: pull_request

	jobs:
	ci-mac-os:
	runs-on: macos-latest

	steps:
	# Clones a single commit from the libtock-rs repository. The commit cloned
	# is a merge commit between the PR's target branch and the PR's source.
	- name: Clone repository
	uses: actions/checkout@v3

	- name: Build and Test
	run: \|
	cd "${GITHUB_WORKSPACE}"
	LIBTOCK_PLATFORM=nrf52 cargo build -p libtock \
	--target=thumbv7em-none-eabi
	LIBTOCK_PLATFORM=hifive1 cargo build -p libtock \
	--target=riscv32imac-unknown-none-elf

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