I tried to build this with the patch on the 4.12.3-2 Debian source and dh_install failed with:
dh_install
cp: cannot stat ‘debian/tmp/usr/lib/libcommanderwidgets.so’: No such file or directory
dh_install: cp -a debian/tmp/usr/lib/libcommanderwidgets.so debian/kommander//usr/lib/ returned exit code 1
/usr/share/pkg-kde-tools/qt-kde-team/2/
dhmk.mk:97: recipe for target 'pre_install_dh_install' failed
make[1]: *** [pre_install_dh_install] Error 2
make[1]: Leaving directory '/pub/deb/kdewebdev-4.12.3'
/usr/share/pkg-kde-tools/qt-kde-team/2/
dhmk.mk:110: recipe for target 'debian/dhmk_install' failed
make: *** [debian/dhmk_install] Error 2