ci: Include tracking of GOOS for which Caddy fails to build (#3617)

* ci: include tracking of GOOS for which Caddy fails to build

* ci: split cross-build check into separate workflow

* ci: cross-build check: make it clear the cross-build check is not a blocker

* ci: cross-build check: set annotation instead of failing the build

* ci: cross-build check: explicitly set continue-on-error to force success marker

* ci: cross-build check: send stderr to /dev/null

* ci: Simplify workflow names

Co-authored-by: Francis Lavoie <lavofr@gmail.com>
Co-authored-by: Francis Lavoie <lavofr@gmail.com>
Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

.github/workflows/ci.yml

@@ -1,6 +1,6 @@
 # Used as inspiration: https://github.com/mvdan/github-actions-golang
 
-name: Cross-Platform
+name: Tests
 
 on:
   push:

.github/workflows/cross-build.yml

@@ -0,0 +1,56 @@
+name: Cross-Build
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  cross-build-test:
+    strategy:
+      fail-fast: false
+      matrix:
+        goos: ['android', 'linux', 'solaris', 'illumos', 'dragonfly', 'freebsd', 'openbsd', 'plan9', 'windows', 'darwin', 'netbsd']
+        go-version: [ 1.14.x ]
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: Print Go version and environment
+        id: vars
+        run: |
+          printf "Using go at: $(which go)\n"
+          printf "Go version: $(go version)\n"
+          printf "\n\nGo environment:\n\n"
+          go env
+          printf "\n\nSystem environment:\n\n"
+          env
+          echo "::set-output name=go_cache::$(go env GOCACHE)"
+      - name: Cache the build cache
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.vars.outputs.go_cache }}
+          key: cross-build-go-${{ matrix.goos }}-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            cross-build-go-${{ matrix.goos }}
+      - name: Checkout code into the Go module directory
+        uses: actions/checkout@v2
+      - name: Run Build
+        env:
+          CGO_ENABLED: 0
+          GOOS: ${{ matrix.goos }}
+        shell: bash
+        continue-on-error: true
+        working-directory: ./cmd/caddy
+        run: |
+          GOOS=$GOOS go build -trimpath -o caddy-"$GOOS"-amd64 2> /dev/null
+          if [ $? -ne 0 ]; then
+            echo "::warning ::$GOOS Build Failed"
+            exit 0
+          fi