This is in preparation of upgrading our library dependencies, some of which
need C++11. We already use C++11 in blender2.8 and for Windows and macOS, so
this just affects Linux.
On many distributions this will not require any changes, on some
install_deps.sh will need to be run again to rebuild libraries.
Differential Revision: https://developer.blender.org/D3568
885cc4cf9a