fixup! gh-127432: Add CI job to cross build Python

Author: matthewhughes934

.github/workflows/build.yml

@@ -525,9 +525,10 @@ jobs:
 
   with-python-build-linux:
     runs-on: ubuntu-latest
-    env:
-      BUILD_DIR: ${{ github.workspace }}/build
     steps:
+      - name: Set build dir
+        run:
+          echo "$BUILD_DIR=$(realpath ${{ github.workspace }}/../build)" >> "$GITHUB_ENV"
       - uses: actions/checkout@v4
         with:
           persist-credentials: false