Run CI on macOS

[iffy]

If you want to, this will run the tests on macOS, too. If you don't want this that's fine, too -- just close it.

[treeform]

We had macOS, but the github runners take way to long to run - like hours and hours. So we decided to disable them.
If only github hard macOS runners that were fast we would enable them.

So we will probably not take this commit PR, sorry.

[iffy]

No worries; I've had to make that same call on other repos for macOS building. FWIW these builds only took 15min, but if there was queue contention, I could see it taking much longer. I'm not offended at all if you close this.

[iffy]

On the latest push, builds for macOS are actually faster than the other ones now: https://github.com/iffy/pixie/actions/runs/3265723604/usage

Though of course there's still possible queue contention for macOS so the start time might be delayed.

Anyway, I'm done fiddling with this, I promise 😄 I'll stop making changes.

[guzba]

We turned macos-latest back on for Puppy and unfortunately it's been extremely slow still (10+minutes to even start sometimes). It makes me not eager to turn this back on for more repos without a specific reason. Puppy uses platform code on so macos-latest makes sense, Pixie does not.

[iffy]

@guzba I see the 10+ minute start time that you're referring to here: https://github.com/treeform/puppy/actions/runs/3935567309/jobs/6734919372

If you look at this PR, rather than using choosenim (via jiro4989/setup-nim-action) to install on macOS which takes 10+ minutes, this PR installs official precompiled binaries (via iffy/install-nim) which takes a few seconds. The reason I even considered adding macOS building to Pixie is because of this macOS-specific issue: #506

[amkrajewski]

Have you tried installing using Homebrew? I found it to behave as expected and during my testing workflow runs it installs nim (v2.0.0) in just about 5s on macos-14 runners or 11s on macos-12 runners.

In my specific case, is also appreciably faster than other runners. Installing (1) nim, (2) Arraymancer and wimpy (through nimble), (3) compiling my code, and (4) running all tests takes under 60s.

To be a bit more quantitative:

Runner	Install Tool	Install Time	Test Runtime
macos-14	Homebrew	5s	16s
ubuntu-latest	jiro4989	7s	30s
macos-12	Homebrew	11s	40s
windows-latest	Conda+jiro4989	185s	51s

There is no magic involved. Here is the job from my workflow YAML file:

test-M1:
    runs-on: macos-14
    steps:
      - name: Checkout
        uses: actions/checkout@v3
      - name: Install Nim with Homebrew
        run: brew install nim
      - name: Install dependencies
        run: nimble install -y arraymancer nimpy
      - name: Compile nimplex
        run: nim c -d:release nimplex.nim
      - name: Run grid tests
        run: nim c -r -d:release tests/runAll.nim

I hope it helps :)