mesa: tune configuration options

GLX can be enabled for the case we support X some day. Also enable sysfs
support.
Use highlighted status macro to report status in scripts

This is more visible than a simple echo. Also only download the L4T root
FS and drivers pack if needed.
Add script to prepare L4T image for OSS graphics stack compilation

prepare-rootfs will perform the following:

- Download and install qemu-static-arm into the target FS to allow to
  run ARM binaries from chroot on an x86 host
- Temporarily replace the target FS's resolv.conf to enable network
  access
- Chroot into the target FS and run apt-get to download the dependencies
  required for the OSS graphics stack compilation
- Fix the absolute libraries symlinks so they can be resolved during
  cross-compilation.
weston: set permissions of weston-launch after install