windeployqt can't create deployment for applications that link to custom Qt modules

Running windeployqt for an application that links custom Qt modules, i.e. Qt modules that aren't part of the Qt itself, fails. It tries to look for those modules from under the Qt. Same problem with libraries that aren't Qt modules that follow the same naming pattern.

For example, build release build of Qt 3D Studio (git clone --recursive https://codereview.qt-project.org/qt3dstudio/qt3dstudio) against a binary release of the Qt 5.11 and install it to a custom directory (make install INSTALL_ROOT=\foo\bar) and then run windeployqt for the installed Qt3DViewer.exe (windeployqt \foo\bar\Qt\5.11.0\msvc2015_64\bin\Qt3DViewer.exe -qmldir=<qt3dstudio repo path>/src/Viewer/Qt3DViewer).

Qt3DViewer.exe links both internal libs named qt3d*.dll and a custom Qt module Qt5Studio3D.dll, none of which actually need to be deployed, because they are already found in the installation directory, but still cause windeployqt to fail.

windeployqt   --qmldir=c:\dev/qt3dstudio/src/Viewer/Qt3DViewer   Qt3DViewer.exe
Unable to find dependent libraries of C:\dev\sdk\Qt/5.10.1\msvc2017_64\bin\qt3dsqmlstreamer.dll :Cannot open 'C:/dev/sdk/Q/5.10.1/msvc2017_64/bin/qt3dsqmlstreamer.dll': The system cannot find the file specified.

or with https://codereview.qt-project.org/226595 :

\windeployqt    --qmldir=c:\dev/qt3dstudio/src/Viewer/Qt3DViewer   Qt3DViewer.exe
Unable to find dependent libraries of C:\dev\sdk\Qt\5.10.1\msvc2017_64\bin\Qt5Studio3D.dll :Cannot open 'C:/dev/sdk/Qt/5.10.1/msvc2017_64/bin/Qt5Studio3D.dll': The system cannot find the file specified.