libraries in /usr/local/lib

[Mikulas Patocka]

Hi

I am maintaining links browser. People complain to me that they can't compile 
it in graphics mode on OpenBSD because it can't find libraries that are placed 
in /usr/local/lib and includes in /usr/local/include.

The problem with libpng can be solved by using pkg-config, problem with libjpeg 
and libtiff can't be solved because you do not distribute .pc files for them.

I'd like to know:

Why does your distribution place libraries and includes to a place where 
compiler can't find them?

What's the correct standard solution for a software developer to find 
libraries? I thought that if gcc -llibrary works, library is presend and if gcc 
-llibrary doesn't work, library isn't present.

It is possible to add -I/usr/local/include -L/usr/local/lib to compiler flags, 
I even distributed links with that for some time, and it turned out that on 
other unix systems -L/usr/local/lib reversed search (first /usr/local/lib and 
then /usr/lib, while it used to be /usr/lib first) and caused linking failures.

Mikulas