I doubt the shebang line in the backend script has any effect now,
since the frontend scripts just source it directly.
v2:
* Use "set -e" instead of adding -e to shebang (Eric Engestrom)
v3:
* Apply to the clang wrapper scripts as well (Eric Engestrom)
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22438>