github: Switched the size-diff pass over to using Meson

.github/workflows/build-pr.yml

@@ -289,12 +289,28 @@ jobs:
     runs-on: ubuntu-22.04
 
     steps:
+      # Build a suitable runtime environment
+      - name: Runtime environment
+        shell: bash
+        env:
+          WORKSPACE: ${{ github.workspace }}
+        # The GITHUB_WORKSPACE step here fixes https://github.com/actions/runner/issues/2058 which is an ongoing issue.
+        run: |
+          echo "$GITHUB_WORKSPACE=`pwd`" >> $GITHUB_ENV
+
       # Setup and use a suitable ARM GCC for the firmware
       - name: Setup ARM GCC
         uses: carlosperate/arm-none-eabi-gcc-action@v1
         with:
           release: '12.2.Rel1'
 
+      # Install and setup a suitable Meson + Ninja
+      - name: Setup Meson + Ninja
+        run: |
+          sudo python3 -m pip install --upgrade pip setuptools wheel
+          sudo python3 -m pip install meson ninja
+        working-directory: ${{ runner.temp }}
+
       - uses: actions/checkout@v4
         with:
           ref: ${{ github.base_ref }}
@@ -305,11 +321,19 @@ jobs:
           ref: ${{ github.event.pull_request.head.sha }}
           path: head
 
+      # Build the base ref firmware for the largest Flash target available
       - name: Build base
-        run: make -C base > base/build.log
+        run: |
+          meson setup build --cross-file=cross-file/blackpill-f411ce.ini
+          meson compile -C build > build.log
+        working-directory: base
 
+      # Build the PR `HEAD` ref firmware for the largest Flash target available
       - name: Build head
-        run: make -C head > head/build.log
+        run: |
+          meson setup build --cross-file=cross-file/blackpill-f411ce.ini
+          meson compile -C build > build.log
+        working-directory: head
 
       - name: Diff
         run: head/scripts/diff_size.py base/build.log head/build.log