CI: integrate macOS

[ChinYikMing]

The current CI pipeline utilizes Linux-based x86-64 and Aarch64 machines for verification and validation (V&V). To enhance the portability of rv32emu, it is both reasonable and feasible to integrate macOS into the CI pipeline.

[ChinYikMing]

A simple CI pipeline for system emulation:

...
+macOS:
+    runs-on: macos-latest
+   steps:
+    - uses: actions/checkout@v4
+    - name: install-dependencies
+      run: |
+            brew install make dtc expect
+    - name: boot Linux kernel test
+      run: |
+            make clean && make ENABLE_SYSTEM=1 && make ENABLE_SYSTEM=1 artifact -j$(sysctl -n hw.logicalcpu)
+            .ci/boot-linux.sh
+            make ENABLE_SYSTEM=1 clean
 ...

[ChinYikMing]

The fetching of the checksum occasionally fails in previous actions(1, 2. 3, ...).

To fully close this issue, the failure should not occur too frequently and the macOS pipeline should be capable of performing V&V for both user and system emulation.

Found at #508

[ChinYikMing]

The occasional failure could be fixed by #536.