Enable GitHub Actions compilation testing

This is a minimal GitHub Actions compilation test for MOM6-examples.  It
primarily only ensures that the model builds after a simple `make -j`
command, without additional configuration.

This can be expanded in the future to include other platforms, as well
as actual model runs and parameter output testing.

.github/actions/macos-setup/action.yml

@@ -0,0 +1,18 @@
+name: 'install-macos-prerequisites'
+
+description: 'Install prerequisites for Mac OS compilation'
+
+runs:
+  using: 'composite'
+
+  steps:
+    - name: Install macOS packages
+      shell: bash
+      run: |
+        echo "::group::Install packages"
+        brew reinstall gcc
+        brew install automake
+        brew install netcdf
+        brew install netcdf-fortran
+        brew install mpich
+        echo "::endgroup::"

.github/actions/ubuntu-setup/action.yml

@@ -0,0 +1,19 @@
+name: 'install-ubuntu-prerequisites'
+
+description: 'Install prerequisites for Ubuntu Linux compilation'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Install Ubuntu Linux packages
+      shell: bash
+      run: |
+        echo "::group::Install linux packages"
+        sudo apt-get update
+        sudo apt-get install netcdf-bin
+        sudo apt-get install libnetcdf-dev
+        sudo apt-get install libnetcdff-dev
+        sudo apt-get install openmpi-bin
+        sudo apt-get install libopenmpi-dev
+        sudo apt-get install linux-tools-common
+        echo "::endgroup::"

.github/workflows/macos-compile.yml

@@ -0,0 +1,24 @@
+name: MacOS Compilation Test
+
+on: [push, pull_request]
+
+jobs:
+  compile:
+
+    runs-on: macOS-latest
+
+    env:
+      CC: gcc
+      FC: gfortran
+
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: recursive
+
+    - uses: ./.github/actions/macos-setup
+
+    - name: Compile models
+      run: make -j
+
+    # TODO: Run a few of the models and compare parameter.doc files?

.github/workflows/ubuntu-compile.yml

@@ -0,0 +1,21 @@
+name: Compile test
+
+on: [push, pull_request]
+
+jobs:
+  compile:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        submodules: recursive
+
+    - uses: ./.github/actions/ubuntu-setup
+
+    # TODO: Split ocean-only and ice-ocean?
+    - name: Compile models
+      run: make -j
+
+    # TODO: Run a few of the models and compare parameter.doc files?