CI: Refactor build type check

Author: rabyj

.github/workflows/build_wheels.yml

@@ -37,36 +37,19 @@ jobs:
           name: pr_number
           path: pr_number.txt
 
-
-  # Build wheels for multiple platforms, and test them, uploading results for reporting.
-  build_wheels:
-    name: Build wheels on ${{ matrix.os }}
-    runs-on: ${{ matrix.os }}
-    env:
-      CI_MATRIX_OS: ${{ matrix.os }} # Unique identifier for test reporting
-    strategy:
-      fail-fast: false # Continue building other platforms if one fails
-      matrix:
-        include:
-          - os: ubuntu-latest
-            cibw_archs: "x86_64 aarch64"
-
-          - os: macos-13 # Intel Mac for x86_64 - could not build without specifying 13.0
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-
-          - os: macos-14 # Apple Silicon - could not build without specifying 14.0
-            cibw_archs: "arm64"
-            deployment_target: "14.0"
-
+  # Explicitly checks branch names and event types
+  # to correctly determine if a full or quick build is needed.
+  determine_build_type:
+    name: Determine Build Strategy
+    runs-on: ubuntu-latest
+    outputs:
+      full_build: ${{ steps.check.outputs.full_build }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
         with:
-          fetch-depth: 0 # full history with tags for setuptools_scm
+          fetch-depth: 0
 
-      # Explicitly checks branch names and event types
-      # to correctly determine if a full or quick build is needed.
       - name: Check if full build needed
         id: check
         run: |
@@ -79,7 +62,6 @@ jobs:
             full_build=true
           elif [[ "${{ github.event_name }}" == "pull_request" ]]; then
             echo "Pull request detected. Checking for C++ file changes."
-            # safer diff for forked PRs
             git fetch origin ${{ github.base_ref }} --depth=1
             if git diff --name-only FETCH_HEAD...HEAD | grep -qE '^(third_party/|epigeec/cc/)'; then
               echo "C++ files were modified. Forcing full build."
@@ -92,16 +74,44 @@ jobs:
           fi
           echo "full_build=$full_build" >> $GITHUB_OUTPUT
 
+  # Build wheels for multiple platforms, and test them, uploading results for reporting.
+  build_wheels:
+    name: Build wheels on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    needs: determine_build_type
+    env:
+      CI_MATRIX_OS: ${{ matrix.os }} # Unique identifier for test reporting
+    strategy:
+      fail-fast: false # Continue building other platforms if one fails
+      matrix:
+        include:
+          - os: ubuntu-latest
+            cibw_archs: "x86_64 aarch64"
+
+          - os: macos-13 # Intel Mac for x86_64 - could not build without specifying 13.0
+            cibw_archs: "x86_64"
+            deployment_target: "13.0"
+
+          - os: macos-14 # Apple Silicon - could not build without specifying 14.0
+            cibw_archs: "arm64"
+            deployment_target: "14.0"
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # full history with tags for setuptools_scm
+
       - name: Set up QEMU (for ARM on Linux)
         if: |
           runner.os == 'Linux' &&
-          steps.check.outputs.full_build == 'true' &&
+          needs.determine_build_type.outputs.full_build == 'true' &&
           contains(matrix.cibw_archs, 'aarch64')
         uses: docker/setup-qemu-action@v3
 
       # Do not set CIBW_BUILD here, let pyproject.toml handle it
       - name: Build wheels (full build)
-        if: steps.check.outputs.full_build == 'true'
+        if: needs.determine_build_type.outputs.full_build == 'true'
         uses: pypa/cibuildwheel@v3.2.1
         with:
           output-dir: dist
@@ -113,7 +123,7 @@ jobs:
       # Set CIBW_BUILD for quick builds (Python 3.11 only)
       - name: Build wheels (quick build)
         if: |
-          steps.check.outputs.full_build == 'false' &&
+          needs.determine_build_type.outputs.full_build == 'false' &&
           (matrix.os == 'ubuntu-latest' || matrix.os == 'macos-14')
         uses: pypa/cibuildwheel@v3.2.1
         with:
@@ -160,7 +170,8 @@ jobs:
   build_sdist:
     name: Build source distribution
     runs-on: ubuntu-latest
-    if: steps.check.outputs.full_build == 'true'
+    needs: determine_build_type
+    if: needs.determine_build_type.outputs.full_build == 'true'
     steps:
       - uses: actions/checkout@v4
         with: