Raspbian Stretch is out for Raspberry Pi. I needed a cross toolchain with the same exact version used to build the system so I built my own. As I had my script ready, I also tried to build one for Mac OS and it seems to work for the moment. I tested these cross toolchains for my projects and seemed to be able to build everything that I tried: Qt libs, apps, omxplayer, ffmpeg etc...
Download Linux x64 cross toolchain GCC 6.3.0 for Stretch here.
Download Mac OS cross toolchain GCC 6.3.0 for Stretch here.
NOTE: The Mac OS version requires some packages to be installed from macports.
NOTE: The toolchain is built to crossbuild for armv7-a. I could also build for armv8 but not sure if it also works for armv6.
Have fun! Bye! ;-)