Add lKUserFeedbackCommon to link flags

This is required to link against static KUserFeedback.

usagestatistic.pro

@@ -3,7 +3,7 @@ DEFINES += USAGESTATISTIC_LIBRARY
 KUSERFEEDBACK_PATH = "$${PWD}/3rdparty/kuserfeedback"
 
 INCLUDEPATH *= "$${KUSERFEEDBACK_PATH}/include" "$${PWD}"
-LIBS *= -L"$${KUSERFEEDBACK_PATH}/lib" -lKUserFeedbackCore -lKUserFeedbackWidgets
+LIBS *= -L"$${KUSERFEEDBACK_PATH}/lib" -lKUserFeedbackCore -lKUserFeedbackWidgets -lKUserFeedbackCommon
 
 CONFIG += c++1z
 QMAKE_CXXFLAGS *= -Wall -Wextra -pedantic