Qt CrossCompile from Linux to Windows with clang-cl and qmake - providing Qt install path

[SebastianM]

Hi,
I've got success with compiling Qt application inside Docker with clang-cl when CMake is used. ie. windows SDK variables are provided through toolchain file and Qt binaries with Qt5_DIR environment variable.

When project uses qmake - I struggle to provide Qt libraries paths.

QT_INSTALL_BINS=/opt/Qt/5.15.0/msvc2015_64 QT_HOST_DATA=/opt/Qt/5.15.0/msvc2015_64 PATH=/usr/lib/llvm-10/bin/:/opt/Qt/5.15.0/msvc2015_64/lib:$PATH qmake -spec /var/nixnote2/linux_win_clang_msvc -d

I've made custom mkspec, but I can't modify Qt install directory. It's taken from QT_HOST_DATE (DEBUG 1: /usr/lib/x86_64-linux-gnu/qt5/mkspecs/features/qt_config.prf:3: QMAKE_QT_CONFIG := /usr/lib/x86_64-linux-gnu/qt5/mkspecs/qconfig.pri), which is Qt internal variable.

Beside OBVIOUS solutions to rewrite project to use CMake - how otherwise can I modify configuration variables?