build/bin/sage-get-system-packages: Substitute PYTHON_MINOR here

Author: Matthias Koeppe

build/bin/sage-get-system-packages

@@ -41,7 +41,7 @@ case "$SYSTEM" in
             fi
         fi
         SYSTEM_PACKAGES_FILE_NAMES="distros/$SYSTEM.txt"
-        STRIP_COMMENTS="sed s/#.*//;"
+        STRIP_COMMENTS="sed s/#.*//;s/\${PYTHON_MINOR}/${PYTHON_MINOR}/g"
         COLLECT=echo
         ;;
 esac