I have a fairly up to date Zig installed via Homebrew.
This is likely the problem. Latest Zig is 0.16 and Ghostty (and therefor Ghostel) require exactly Zig 15.2.
I just updated our code to have a better error message and make it clear that the problem is the Zig version. See https://github.com/dakra/ghostel/pull/541
jFYI, Ghostty issue to support 0.16 is here: https://github.com/ghostty-org/ghostty/issues/12228
So for your homebrew zig you probably have to:
brew uninstall zig
brew install zig@0.15