I found this out when trying to compile znc-extra while doing a single-user install (non make install). The znc-extra doesn't include the .h files that it needs for compiling most of its modules. To fix this get a version of znc-0.068 in a directory then...
cp znc-config /path/to/znc-extra
cp *.h /path/to/znc-extra
chmod +x znc-config (you may have to do this)
This will copy over the znc-config file and any file ending in .h to your znc-extra and then you are able to make the znc-extra modules fine.
Cheers,
Hope this helped you out
Why is this filed as a patch with category widget? Oo
Anyway, starting with znc 0.070, znc installs a pkg-config control file (znc.pc). For some days the znc-extra configure script now uses pkg-config instead of znc-config.
pkg-config got a nice feature that if you ask for x and it finds x-uninstalled, then it uses the uninstalled file. ZNC generates such a file in the source dir which makes the following work fine:
./configure PKG_CONFIG_PATH=/path/to/znc/source/dir/
Closing since the next release will sort this out. (One only has to know about $PKG_CONFIG_PATH so that pkg-config finds the right files...)