MacOS Catalina 10.15.5 compilation error

[che85 (Christian Herz)]

@pieper

cmake \
	-DCMAKE_OSX_DEPLOYMENT_TARGET=10.15 \
	Qt5_VERSION:STRING=5.15 \
	Qt5_DIR:PATH=/usr/local/Cellar/qt/5.15.0/lib/cmake/Qt5 \

Similar to yours:

cmake \
-DCMAKE_OSX_DEPLOYMENT_TARGET=10.15 \
-DQt5_VERSION:STRING=5.15 \
-DQt5_DIR:PATH=/usr/local/Cellar/qt/5.15.0/lib/cmake/Qt5 \
~/sources/cpp/Slicer