No dynamic libraries on Mac OS X

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

After several days of pkgsrc building, I noticed that all of the libraries were 
only installed as static versions and there is no single .dylib under 
/usr/pkg/lib.
I first thought that was a clang problem, but setting PKGSRC_COMPILER to gcc 
exhibits the same behaviour.

For instance, devel/readline says
checking configuration for building shared libraries... supported
but only installs lib{history|readline}.{a|la}.

Is this known issue? I'm on 2010Q1, 10.5.0 and Xcode 3.2.5