mach: recreate .venv when .python-version changes (#34712)

The new images published in servo/ci-runners#12 should have `uv`
installed already and the initial build of servo triggered during the
base image construction will force the installation of the Python
version mentioned at the time of the image construction (3.12). When
.python-version changes, we can no longer use the .venv baked into the
image and must recreate the it to avoid activating the environment.

Signed-off-by: Mukilan Thiyagarajan <mukilan@igalia.com>

.github/workflows/mac.yml

@@ -80,18 +80,18 @@ jobs:
         run: cargo install --path support/crown
       - name: Bootstrap
         run: |
-          python3 ./mach bootstrap --skip-lints
+          ./mach bootstrap --skip-lints
           brew install gnu-tar
       - name: Build (${{ inputs.profile }})
         run: |
-          python3 ./mach build --use-crown --locked --${{ inputs.profile }}
+          ./mach build --use-crown --locked --${{ inputs.profile }}
           cp -r target/cargo-timings target/cargo-timings-macos
       - name: Smoketest
         uses: nick-fields/retry@v3
         with: # See https://github.com/servo/servo/issues/30757
           timeout_minutes: 5
           max_attempts: 2
-          command: python3 ./mach smoketest --${{ inputs.profile }}
+          command: ./mach smoketest --${{ inputs.profile }}
       - name: Script tests
         run: ./mach test-scripts
       - name: Unit tests
@@ -100,9 +100,9 @@ jobs:
         with:
           timeout_minutes: 40 # https://github.com/servo/servo/issues/30275
           max_attempts: 3 # https://github.com/servo/servo/issues/30683
-          command: python3 ./mach test-unit --${{ inputs.profile }}
+          command: ./mach test-unit --${{ inputs.profile }}
       - name: Build mach package
-        run: python3 ./mach package --${{ inputs.profile }}
+        run: ./mach package --${{ inputs.profile }}
       - name: Run DMG smoketest
         uses: nick-fields/retry@v3
         with: # See https://github.com/servo/servo/issues/30757
@@ -123,7 +123,7 @@ jobs:
       - name: Upload nightly
         if: ${{ inputs.upload }}
         run: |
-          python3 ./mach upload-nightly mac --secret-from-environment \
+          ./mach upload-nightly mac --secret-from-environment \
             --github-release-id ${{ inputs.github-release-id }}
         env:
           S3_UPLOAD_CREDENTIALS: ${{ secrets.S3_UPLOAD_CREDENTIALS }}