ci: add build to SAGE

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

.github/workflows/ci-sage.yml

@@ -109,7 +109,7 @@ jobs:
       # Extra packages to install as system packages
       extra_sage_packages: "liblzma bzip2 libffi libpng python3 ninja_build"
       # Sage distribution packages to build
-      targets: SAGE_CHECK=no SAGE_CHECK_PACKAGES="meson_python" meson_python
+      targets: SAGE_CHECK=no SAGE_CHECK_PACKAGES="meson_python" python_build meson_python
       # Standard setting: Test the current beta release of Sage:
       sage_repo: sagemath/sage
       sage_ref: develop