plugins/contacts/maemo5/maemo5.pro does

CONFIG += link_pkgconfig
PKGCONFIG += libosso-abook-1.0

However, this does not validate that the appropriate .pc file is present. This leads to this output while running qmake:

Package libosso-abook-1.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `libosso-abook-1.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libosso-abook-1.0' found
Package libosso-abook-1.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `libosso-abook-1.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libosso-abook-1.0' found
Package libosso-abook-1.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `libosso-abook-1.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libosso-abook-1.0' found

No error happens though and compilation fails due to indirect dependencies not being met.

In file included from /home/user/src/messaging/plugins/contacts/maemo5/qcontactmaemo5backend_p.h:56,
from /home/user/src/messaging/plugins/contacts/maemo5/qcontactabook.cpp:42:
/home/user/src/messaging/plugins/contacts/maemo5/qcontactabook_p.h:51:35: error: gdk-pixbuf/gdk-pixbuf.h: No such file or directory
snip lots and lots of useless errors

How could this be improved? configure would ideally stop and let me know which packages were missing (or at least which .pc files were missing). At build time, the build system could detect the missing .pc files and fail in a way that makes sense instead of letting the compile go ahead.