FTBFS qtwebengine: ../build/gen.py No such file or directory

cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_INSTALL_LIBDIR=lib -DCMAKE_BUILD_TYPE=MinSizeRel -DCMAKE_FIND_FRAMEWORK=LAST -DCMAKE_VERBOSE_MAKEFILE=ON -Wno-dev -DBUILD_TESTING=OFF -DCMAKE_OSX_SYSROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX11.sdk -D CMAKE_STAGING_PREFIX=/usr/local/Cellar/qt-web-engine/6.2.0-rc2 -S . -G Ninja

cmake --build .

 [0/1] Generating gn ninja: Entering directory `/tmp/qt-web-engine-20210926-11686-167fi4q/qtwebengine-everywhere-src-6.2.0-rc2/src/gn/Release' [1/1] Regenerating ninja files FAILED: build.ninja 3114/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python ../build/gen.py 3115/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: can't open file '../build/gen.py': [Errno 2] No such file or directory 3116ninja: error: rebuilding 'build.ninja': subcommand failed