Qt compile causes files to be placed outside specified folder

I want to separately compile a Qt debug and Qt release version with two different configurations:

I create a folder
c:\dev\3pp\Qt\Src\build_release_5_15_0

and I do this configure:

..\configure --prefix=%CD%/qtbase -release -opensource -confirm-license -force-debug-info -separate-debug-info -qt-libjpeg -qt-libpng -qt-sqlite -nomake examples -nomake tests -no-dbus -platform win32-msvc2019 -make-tool jom -opengl desktop -no-qml-debug -skip qtconnectivity -skip qtwebview -skip qtdatavis3d -skip qtgamepad -skip qtscript -skip qt3d -skip qtdoc -skip qtactiveqt -skip qtwebglplugin -skip qtquick3d -skip qtspeech -skip qtdoc

and I do a successful build, but afterwards I have a folder
c:\dev\3pp\Qt\Src\build_debug_5_15_0, which I actually wanted to use for debug build.

Then I can create another debug folder, but it has stolen my most obvious name, and the debug build also causes a release folder to be made, so the confusion when looking at folder names becomes complete.

I would strongly prefer to stay inside the folder specified and if impossible then at least prevent stealing the obvious name for the opposite debug/release build.

(Currently I don't even know if I safely can remove the 'wrong' folders)