[llvm] [workflows] Port buildkite Windows config to GitHub actions (PR #82093)

[Mehdi Amini via llvm-commits]

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@@ -0,0 +1,61 @@
+name: "Windows Precommit Tests"
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    branches:
+      - main
+
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: only if it is a pull request build.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
+jobs:
+  build-llvm-windows:
+    name: "Build and test LLVM (Windows)"
+    runs-on: windows-2022
+    steps:
+      - name: Setup Windows
+        uses: llvm/actions/setup-windows at main
+        with:
+          arch: amd64
+      - name: Fetch LLVM sources
+        uses: actions/checkout at v4
+        with:
+          fetch-depth: 2
+      - name: Setup ccache
+        uses: hendrikmuhs/ccache-action at v1
+        with:
+          max-size: 500M
+          variant: sccache
+          key: precommit-windows
+      - name: Compute projects to test
+        id: compute-projects
+        uses: ./.github/workflows/compute-projects-to-test
+        with:
+          projects: clang llvm lld
+
+      - name: Configure LLVM
+        shell: bash
+        if: ${{ steps.compute-projects.outputs.check-targets }}
+        run: |
+          cmake -B build -GNinja \
+            -DCMAKE_BUILD_TYPE=Release \
+            -DLLVM_ENABLE_PROJECTS="${{ steps.compute-projects.outputs.projects }}" \
+            -DCMAKE_C_COMPILER_LAUNCHER=sccache \
+            -DCMAKE_CXX_COMPILER_LAUNCHER=sccache \
+            -DLLVM_ENABLE_ASSERTIONS=ON \
+            -DLLVM_LIT_ARGS="-v --no-progress-bar" \
+            -S llvm
+      - name: Build LLVM
+        if: ${{ steps.compute-projects.outputs.check-targets }}
+        run: |
+          ninja -C build test-depends
----------------
joker-eph wrote:

This step will overbuild: if a PR only touches clang and not LLVM, it should only run `ninja check-clang` and not build the LLVM unit-tests and other things not needed by clang for example.
(same for the other projects)

```suggestion
```

https://github.com/llvm/llvm-project/pull/82093