Port to L4T (Linux for Tegra).

A first pass port to L4T that builds the essentials, with these
important caveats:

- the replayer crashes after the first frame of a test D3 trace
- the chroot scripts have only a cursory pass to support ARM targets
- mkvogl.cpp needs to be fixed up for the ARM support added to cmake
- libbacktrace cmake config needs to be unhacked

The chroot is partially manually configured, and the build is
currently still invoked manually.