Installing Postgresql parray_gin extension on mac, include not found
You need to manually download the sources and edit the Makefile

Add this:

PG_CPPFLAGS = "-I/usr/local/opt/icu4c/include"
SHLIB_LINK =  "-L/usr/local/opt/icu4c/lib"


and it works

https://github.com/theirix/parray_gin/issues/5