[firebird-support] Error (ICU development package not installed) compiling latest Firebird sources on FreeBSD 11.2 system

[sfale...@gmail.com [firebird-support]]

I am getting the error when compiling on a fully updated FreeBSD 11.2 system 
(by running ./configure). I've also installed the ICU development package, but 
the error recurs. Does anyone have an idea how to fix this, please?