"ming32-make clean" removes import libs

I built shared Qt 5.6.0 from source, build successfully. and after I run mingw32-make clean, the makefile qmake generated does not work anymore. and I found all the .prl files have wrong value of QMAKE_PRL_TARGET. when I track the code, the issue is qmake.

file $qt/qtbase/qmake/generators/win32/winmakefile.cpp line 236-238. these lines are new added from qt 5.5.1. and even CONFIG is shared the LIB_TARGET contains QMAKE_PREFIX_STATICLIB and QMAKE_EXTENSION_STATICLIB. these line should be like the line 245

project->values("LIB_TARGET").prepend(project->first("TARGET") + project->first("TARGET_EXT"));

one more question, if I want to submit my code and merge to qt code, what should I do? thanks