Build release binaries for multiple targets

This adds release binary builds for the 4 platforms currently supported
by the free GitHub Action runners:

* Linux x86_64
* Windows x86_64
* Mac x86_64
* Mac AArch64

The test stages for these are known to fail, but the creating and
upoading of the release binaries should pass.

.github/workflows/release-binaries-all.yml

@@ -0,0 +1,94 @@
+name: Release Binaries All
+
+permissions:
+  contents: read # Default everything to read-only
+
+on:
+  workflow_dispatch:
+    inputs:
+      release-version:
+        description: 'Release Version'
+        required: true
+        type: string
+      upload:
+        description: 'Upload binaries to the release page'
+        required: true
+        default: false
+        type: boolean
+
+  workflow_call:
+    inputs:
+      release-version:
+        description: 'Release Version'
+        required: true
+        type: string
+      upload:
+        description: 'Upload binaries to the release page'
+        required: true
+        default: false
+        type: boolean
+
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      # When a PR is closed, we still start this workflow, but then skip
+      # all the jobs, which makes it effectively a no-op.  The reason to
+      # do this is that it allows us to take advantage of concurrency groups
+      # to cancel in progress CI jobs whenever the PR is closed.
+      - closed
+    paths:
+      - '.github/workflows/release-binaries-all.yml'
+      - '.github/workflows/release-binaries.yml'
+      - '.github/workflows/release-binaries-setup-stage/*'
+      - '.github/workflows/release-binaries-save-stage/*'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || 'dispatch' }}
+  cancel-in-progress: True
+
+jobs:
+  setup-variables:
+    if: >-
+      (github.event_name != 'pull_request' || github.event.action != 'closed')
+    runs-on: ubuntu-22.04
+    outputs:
+      release-version: ${{ steps.vars.outputs.release-version }}
+      upload: ${{ steps.vars.outputs.upload }}
+    steps:
+      - shell: bash
+        id: vars
+        run: |
+          upload="${{ inputs.upload }}"
+          release_version="${{ inputs.release-version }}"
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            upload="false"
+            release_version=""
+          fi
+          echo "release-version=$release_version" >> "$GITHUB_OUTPUT"
+          echo "upload=$upload" >> "$GITHUB_OUTPUT"
+
+  release-binaries-all:
+    name: Build Release Binaries
+    needs:
+      - setup-variables
+    permissions:
+      contents: write # For release uploads
+      id-token: write     # For artifact attestations
+      attestations: write # For artifact attestations
+    strategy:
+      fail-fast: false
+      matrix:
+        runs-on:
+          - ubuntu-22.04
+          - windows-2022
+          - macos-13
+          - macos-14
+
+    uses: ./.github/workflows/release-binaries.yml
+    with:
+      release-version: "${{ needs.setup-variables.outputs.release-version }}"
+      upload: ${{ needs.setup-variables.outputs.upload == 'true'}}
+      runs-on: "${{ matrix.runs-on }}"
+

.github/workflows/release-binaries-save-stage/action.yml

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+name: Save Stage
+inputs:
+  build-prefix:
+    description: "Directory containing the build directory."
+    required: true
+    type: 'string'
+
+runs:
+  using: "composite"
+  steps:
+    # We need to create an archive of the build directory, because it has too
+    # many files to upload.
+    - name: Package Build and Source Directories
+      shell: bash
+      run: |
+        # Windows does not support symlinks, so we need to dereference them.
+        tar --exclude build/ ${{ (runner.os == 'Windows' && '-h') || '' }} -c . | zstd -T0 -c > ../llvm-project.tar.zst
+        mv ../llvm-project.tar.zst .
+        tar -C ${{ inputs.build-prefix }} -c build/ | zstd -T0 -c > build.tar.zst
+
+    - name: Upload Stage 1 Source
+      uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 #v4.3.0
+      with:
+        name: ${{ runner.os }}-${{ runner.arch }}-${{ github.job }}-source
+        path: llvm-project.tar.zst
+        retention-days: 2
+
+    - name: Upload Stage 1 Build Dir
+      uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 #v4.3.0
+      with:
+        name: ${{ runner.os}}-${{ runner.arch }}-${{ github.job }}-build
+        path: build.tar.zst
+        retention-days: 2

.github/workflows/release-binaries-setup-stage/action.yml

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+name: Setup Stage
+
+inputs:
+  previous-artifact:
+    description: >-
+      A unique descriptor for the artifact from the previous stage.  This will
+      be used to construct the final artifact pattern, which is:
+      $RUNNER_OS-$RUNNER_ARCH-$PREVIOUS_ARTIFACT-*
+    required: false
+    type: 'string'
+
+outputs:
+  build-prefix:
+    description: "Directory containing the build directory."
+    value: ${{ steps.build-prefix.outputs.build-prefix }}
+
+runs:
+  using: "composite"
+  steps:
+    - name: Install Ninja
+      uses: llvm/actions/install-ninja@22e9f909d35b50bd1181709564bfe816eaeaae81 # main
+
+    - name: Setup Windows
+      if: startsWith(runner.os, 'Windows')
+      uses: llvm/actions/setup-windows@main
+      with:
+        arch: amd64
+
+    - name: Set Build Prefix
+      id: build-prefix
+      shell: bash
+      run: |
+        build_prefix=`pwd`
+        if [ "${{ runner.os }}" = "Linux" ]; then
+          sudo chown $USER:$USER /mnt/
+          build_prefix=/mnt/
+        fi
+        echo "build-prefix=$build_prefix" >> $GITHUB_OUTPUT
+
+    - name: Download Prevous Stage Artifact
+      if: ${{ inputs.previous-artifact }}
+      id: download
+      uses: actions/download-artifact@6b208ae046db98c579e8a3aa621ab581ff575935 # v4.1.1
+      with:
+        pattern: ${{ runner.os }}-${{ runner.arch }}-${{ inputs.previous-artifact }}-*
+        merge-multiple: true
+
+    - name: Unpack Artifact
+      if: ${{ steps.download.outputs.download-path }}
+      shell: bash
+      run: |
+        tar --zstd -xf llvm-project.tar.zst
+        rm llvm-project.tar.zst
+        tar --zstd -C ${{ steps.build-prefix.outputs.build-prefix}} -xf build.tar.zst
+        rm build.tar.zst