jit: Fix warning reported by gcc-11 caused by dubious function signature.
Reported-By: Erik Rijkers <er@xs4all.nl>
Discussion: https://postgr.es/m/
833107370.
1313189.
1619647621213@webmailclassic.xs4all.nl
Backpatch: 13, where
b059d2f45685 introduced the issue.