[win32, MinGW] Qt5 does not find external libraries that works in Qt4

[sylvaticus]

Hello, I do my main development in Linux and time to time (years) I do a compilation in Windows.

In my windows machine I had Qt 4.8 with gcc 4.6. I compiled, long time ago and using gcc 4.6, some external libraries and my old code works fine.
Now I wanted to compile in windows my new code, that in the meantime has been ported to Qt5.
So in the windows machine I installed, in an other folder, Qt5, that now comes shipped directly each version of Qt with its own MinGW. For example I have Qt5.2.1 with its DOS prompt set to work with gcc 4.8.

My project uses some external libraries that have been compiled from source in windows using gcc 4.6 (and it was a mess, so I would really like to avoid to recompile them if possible).

My qt project file instructs the linker to use them with the following lines:

win32 {
    INCLUDEPATH += win32/include/coin
    INCLUDEPATH += win32/include/coin/ThirdParty
    INCLUDEPATH += win32/include
    INCLUDEPATH += win32/include/adolc
    INCLUDEPATH += $$[QT_INSTALL_DATA]/src/3rdparty/zlib
    LIBS += -L win32/lib -lipopt
    LIBS += -L win32/lib -lcoinmetis
    LIBS += -L win32/lib -lcoinmumps
    LIBS += -L win32/lib -lcoinhsl
    LIBS += -L win32/lib -lcoinblas
    LIBS += -L win32/lib -lcoinlapack
    LIBS += -L win32/lib -ladolc
    LIBS += -lpthread -lgfortran -lcoinmetis -lcoinblas
    CONFIG += exceptions
}

win32 {
    INCLUDEPATH += win32/include/coin
    INCLUDEPATH += win32/include/coin/ThirdParty
    INCLUDEPATH += win32/include
    INCLUDEPATH += win32/include/adolc
    INCLUDEPATH += $$[QT_INSTALL_DATA]/src/3rdparty/zlib
    LIBS += -L win32/lib -lipopt
    LIBS += -L win32/lib -lcoinmetis
    LIBS += -L win32/lib -lcoinmumps
    LIBS += -L win32/lib -lcoinhsl
    LIBS += -L win32/lib -lcoinblas
    LIBS += -L win32/lib -lcoinlapack
    LIBS += -L win32/lib -ladolc
    LIBS += -lpthread -lgfortran -lcoinmetis -lcoinblas
    CONFIG += exceptions
}

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The problem is that when I run make, I got, in Qt5, the following error:
screenshot _qt5.jpg

When I run the old software, with the same configuration and using the Qt4 prompt, I don't have instead any linking problem:
screenshot_qt4.png

Could it be a different way of including external libraries in a project in Qt5 compared to Qt4? Or because the external libraries have been compiled with gcc 4.6 and are hence not recognised by the gcc 4.8 used with the new Qt5 ??

[Lesiok]

On first screenshot I see "permission denied" error.