lib.pro is a *.pro-file for qmake

It produces static lib (libqtermwidget.a) only. 
For creating shared lib (*.so) uncomment "dll" in "CONFIG" line in *.pro-file

Library was tested both with HAVE_POSIX_OPENPT and HAVE_GETPT precompiler directives, 
defined in "DEFINES" line. You should select variant which would be correct for your system.