Created new file src/gui/macutilities.mm, moved code from mainwindow.cpp and torrentcontentmodel.cpp that used the Objective C runtime into it and converted it to actual Objective C. Rewrote pixmapForExtension() so that it doesn't call into private Qt functions.
Qt resource is innitialized by a static object constructor (see
https://wiki.qt.io/QtResources). When we put resources into a static
library, the linker removes that static objects and thus the resources
themselves. To correct that we append resources to the main executable
sources list. This is done via custom function qbt_target_sources which
knows where to read the executable' name.
Brian Kendall