Unable to build Quick MultiEffect examples - "... is lacking an install target"

[Name already in use]

Hello,

I cloned the Quick MultiEffect extension from git://code.qt.io/qt-extensions/qtquickmultieffect.git. But when I open the .pro file of any example, QtCreator gives me the error
Project ERROR: [path/to/.pro/file] is lacking an install target
I am using the Desktop Qt 5.15.2 MinGW 64-bit kit.
What can I do to to resolve this error?

[jsulm]

@Name-already-in-use Can you post the pro file from that project?

[john_duan]

This post is deleted!

[john_duan]

@jsulm
Hello, code in QuickMultiEffect.pro

# Add this into include path
INCLUDEPATH += $$PWD/

load(qt_parts)

doc.file = doc/doc.pro
SUBDIRS += doc