Add BUNDLE DESTINATION to CMakeLists.txt
Created by: nickgarvey
Without it:
grace:build ngarvey$ cmake -DCMAKE_BUILD_TYPE=Release -DQt5Widgets_DIR=/usr/local/opt/qt5/lib/cmake/Qt5Widgets ..
CMake Error at heimdall-frontend/CMakeLists.txt:53 (install):
install TARGETS given no BUNDLE DESTINATION for MACOSX_BUNDLE executable
target "heimdall-frontend".
Reason: https://cmake.org/cmake/help/v3.0/policy/CMP0006.html