ci: switch to GitHub Actions for Windows builds

GitHub Actions is faster and much better integrated into GitHub than
Azure Pipelines, and is in general easier to use. Therefore, switch to
GitHub Actions for our Windows builds and tests.

.github/workflows/windows.yml

@@ -0,0 +1,85 @@
+name: Windows
+
+on: push
+
+jobs:
+  build-windows:
+    runs-on: windows-2016
+    steps:
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: '1.17'
+      - name: Install QEMU
+        shell: bash
+        run: |
+          choco install qemu --version=2020.06.12
+          echo "C:\Program Files\QEMU" >> $GITHUB_PATH
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          submodules: true
+      - name: Cache LLVM source
+        uses: actions/cache@v2
+        id: cache-llvm-source
+        with:
+          key: llvm-source-11-windows-v1
+          path: |
+            llvm-project/clang/lib/Headers
+            llvm-project/clang/include
+            llvm-project/lld/include
+            llvm-project/llvm/include
+      - name: Download LLVM source
+        if: steps.cache-llvm-source.outputs.cache-hit != 'true'
+        run: make llvm-source
+      - name: Cache LLVM build
+        uses: actions/cache@v2
+        id: cache-llvm-build
+        with:
+          key: llvm-build-11-windows-v2
+          path: llvm-build
+      - name: Build LLVM
+        if: steps.cache-llvm-build.outputs.cache-hit != 'true'
+        shell: bash
+        run: |
+          # fetch LLVM source
+          rm -rf llvm-project
+          make llvm-source
+          # install dependencies
+          choco install ninja
+          # build!
+          make llvm-build
+          # Remove unnecessary object files (to reduce cache size).
+          find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
+      - name: Cache wasi-libc sysroot
+        uses: actions/cache@v2
+        id: cache-wasi-libc
+        with:
+          key: wasi-libc-sysroot-v1
+          path: lib/wasi-libc/sysroot
+      - name: Build wasi-libc
+        if: steps.cache-wasi-libc.outputs.cache-hit != 'true'
+        run: make wasi-libc
+      - name: Test TinyGo
+        shell: bash
+        run: make test
+      - name: Build TinyGo release tarball
+        run: make build/release -j4
+      - name: Make release artifact
+        shell: bash
+        working-directory: build/release
+        run: 7z -tzip a release.zip tinygo
+      - name: Publish release artifact
+        # Note: this release artifact is double-zipped, see:
+        # https://github.com/actions/upload-artifact/issues/39
+        # We can essentially pick one of these:
+        # - have a dobule-zipped artifact when downloaded from the UI
+        # - have a very slow artifact upload
+        # We're doing the former here, to keep artifact uploads fast.
+        uses: actions/upload-artifact@v2
+        with:
+          name: release-double-zipped
+          path: build/release/release.zip
+      - name: Smoke tests
+        shell: bash
+        run: make smoketest TINYGO=build/tinygo AVR=0 XTENSA=0

azure-pipelines.yml

@@ -1,88 +0,0 @@
-# Avoid lengthy LLVM rebuilds on each newly pushed branch. Pull requests will
-# be built anyway.
-trigger:
-- release
-- dev
-
-jobs:
-- job: Build
-  timeoutInMinutes: 240 # 4h
-  pool:
-    vmImage: 'VS2017-Win2016'
-  steps:
-    - task: GoTool@0
-      inputs:
-        version: '1.17'
-    - checkout: self
-      fetchDepth: 1
-    - task: Cache@2
-      displayName: Cache LLVM source
-      inputs:
-        key: llvm-source-11-windows-v1
-        path: llvm-project
-    - task: Bash@3
-      displayName: Download LLVM source
-      inputs:
-        targetType: inline
-        script: make llvm-source
-    - task: CacheBeta@0
-      displayName: Cache LLVM build
-      inputs:
-        key: llvm-build-11-windows-v5
-        path: llvm-build
-    - task: Bash@3
-      displayName: Build LLVM
-      inputs:
-        targetType: inline
-        script: |
-          if [ ! -f llvm-build/lib/liblldELF.a ]
-          then
-            # install dependencies
-            choco install ninja
-            # hack ninja to use fewer jobs
-            echo -e 'C:\\ProgramData\\Chocolatey\\bin\\ninja -j4 %*' > /usr/bin/ninja.bat
-            # build!
-            make llvm-build
-          fi
-    - task: Bash@3
-      displayName: Install QEMU
-      inputs:
-        targetType: inline
-        script: choco install qemu --version=2020.06.12
-    - task: CacheBeta@0
-      displayName: Cache wasi-libc sysroot
-      inputs:
-        key: wasi-libc-sysroot-v4
-        path: lib/wasi-libc/sysroot
-    - task: Bash@3
-      displayName: Build wasi-libc
-      inputs:
-        targetType: inline
-        script: PATH=/usr/bin:$PATH make wasi-libc
-    - task: Bash@3
-      displayName: Test TinyGo
-      inputs:
-        targetType: inline
-        script: |
-          export PATH="$PATH:./llvm-build/bin:/c/Program Files/qemu"
-          unset GOROOT
-          make test
-    - task: Bash@3
-      displayName: Build TinyGo release tarball
-      inputs:
-        targetType: inline
-        script: |
-          export PATH="$PATH:./llvm-build/bin:/c/Program Files/qemu"
-          unset GOROOT
-          make build/release -j4
-    - publish: $(System.DefaultWorkingDirectory)/build/release/tinygo
-      displayName: Publish zip as artifact
-      artifact: tinygo
-    - task: Bash@3
-      displayName: Smoke tests
-      inputs:
-        targetType: inline
-        script: |
-          export PATH="$PATH:./llvm-build/bin:/c/Program Files/qemu"
-          unset GOROOT
-          make smoketest TINYGO=build/tinygo AVR=0 XTENSA=0