Add caching of the installed cross binary

action.yml

@@ -44,16 +44,37 @@ runs:
       with:
         targets: ${{ inputs.target }}
         toolchain: ${{ inputs.toolchain }}
+    - name: Determine latest cross version
+      id: determine-latest-cross-version
+      shell: bash
+      run: determine-latest-cross-version.sh
+      env:
+        GITHUB_TOKEN: ${{ inputs.GITHUB_TOKEN }}
+      if: ${{ steps.determine-cross-compile.outputs.needs-cross == 'true' }}
+    # We need to accesss this in both this YAML config and shell scripts. It
+    # doesn't seem like using ${{ env.RUNNER_TEMP }} works in the YAML config.
+    - name: Set directory for installing cross
+      id: set-cross-dir
+      shell: bash
+      run: set-cross-dir.sh
+      if: ${{ steps.determine-cross-compile.outputs.needs-cross == 'true' }}
+    - name: Cache cross
+      id: cache-cross
+      uses: actions/cache@v3
+      with:
+        path: ${{ steps.set-cross-dir.outputs.cross-dir }}/cross
+        key: ${{ runner.os }}-${{ steps.determine-latest-cross-version.outputs.cross-version }}
+      if: ${{ steps.determine-cross-compile.outputs.needs-cross == 'true' }}
     - name: Install cross if cross-compiling (*nix)
       shell: bash
-      run: install-cross-nix.sh
-      if: ${{ steps.determine-cross-compile.outputs.needs-cross == 'true' }}
+      run: install-cross-nix.sh ${{ steps.set-cross-dir.outputs.cross-dir }}
+      if: ${{ steps.determine-cross-compile.outputs.needs-cross == 'true' && steps.cache-cross.outputs.cache-hit != 'true' }}
       env:
         GITHUB_TOKEN: ${{ inputs.GITHUB_TOKEN }}
     - name: Set build command
       id: set-build-command
       shell: bash
-      run: set-build-command.sh
+      run: set-build-command.sh ${{ steps.set-cross-dir.outputs.cross-dir }}
     - name: Run tests (*nix)
       shell: bash
       run: |