HEADERS should list only the files that your code, not external libraries.

You have told qmake that a file called hdl.h exists in your project (in the same place as the pro file) and needs to be pre-processed for Q_OBJECT macros etc. Qmake has dutifully written a make file rule to do that. This file does not exist in your code, and is not generated by another rule in the file, so that make rule fails when executed.

Save yourself some other possible problems and use absolute or drive relative paths in the LIBS and INCLUDEPATH. Variables.