nixos/postgresql: fix enableJIT

Make sure that JIT is actually available when using

    services.postgresql = {
      enable = true;
      enableJIT = true;
      package = pkgs.postgresql_15;
    };

The current behavior is counter-intuitive because the docs state that
`enableJIT = true;` is sufficient even though it wasn't in that case
because the declared package doesn't have the LLVM dependency.

Fixed by using `package.withJIT` if `enableJIT = true;` and
`package.jitSupport` is `false`.

Also updated the postgresql-jit test to test for that case.

0 files changed, 0 insertions, 0 deletions