If project have DEF_FILE set in .pro file, then that file(.def) is searched at wrong location(-build dir) instead of dir set in DEF_FILE.
If I manually copy def file to '-build' dir then compiling is ok

compile output looks like this:
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c:/qt/qtcreator-1.3.83/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: def-file_bug.def: No such file: No such file or directory
collect2: ld returned 1 exit status
mingw32-make[1]: *** [debug\def-file_bug.dll] Error 1
mingw32-make: *** [debug] Error 2
Exited with code 2.
Error while building project def-file_bug (target: Desktop)
When executing build step 'Make'
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take a look at attachment.