There's a merged pull request on the void-packages repository

ponyc: update to 0.33.2.
https://github.com/void-linux/void-packages/pull/18748

Description:
Updated to LLVM 9 now that ponyc uses it.

Adds which as the makefile uses it regardless of whether LLVM_CONFIG is
set, resulting in an error because it cannot find an llvm-config.