After installing the crystal package on a fresh system, you can't really use the language because linking a program fails:

$ pacman -S crystal
$ crystal eval 'puts "Hello World"!
--: line 1: cc: command not found
Error: execution of command failed with code: 127: `cc "${@}" -o /root/.cache/crystal/crystal-run-eval.tmp -rdynamic -L/usr/bin/../lib/crystal -lpcre -lm -lgc -lpthread -levent -lrt -ldl`

Building a Crystal program requires a linker is available (`cc` or anything else configured via `CC` env var). Without a linker, the package is mostly unusable.

I think the package should depend on `gcc` or any other package that provides a suitable linker. Technically, you don't need `gcc` if you have say a different linker installed. Not sure if there are solutions for this in PKGBUILD (such as virtual packages). But a hard dependency on `gcc` is better than having no linker available.