* Detect kernel rcu_sched stall + cosmetic improvements
* Start QEMU with options '-nographic -monitor none'. Without this,
QEMU cannot be run on the Travis servers which have no display.
'-monitor none' is needed when '-nographic' is set and one wants to
redirect serial port 0 (first occurrence of '-serial stdio'), otherwise
a conflict occurs and the following message is shown:
    qemu-system-arm: -serial stdio: cannot use stdio by multiple character
    devices
* Fix undefined variable error on timeout
* Set LD_LIBRARY_PATH. The libraries that come with the compiler
sometimes end up under /lib, or under /lib/arm-linx-gnueabihf. By setting
LD_LIBRARY_PATH we support both.
* Catch kernel panic/timeout on boot to make the script more robust.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>

Adds an Expect script to launch QEMU, run xtest and return a pass/fail
status. This makes it even easier to launch non-regression tests and
possibly integrate into a CI loop.

The script may be invoked through 'make check' or 'make check-only'.
The former considers dependencies, while the latter just runs the script.

The output of serial ports 0 and 1 are saved to serial0.log and
serial1.log, respectively.

Expect may be installed with 'sudo apt-get install expect' on Debian/
Ubuntu distributions.

Sample output:

 $ make -j9 check
 <snip>
 expect qemu-check.exp -- \
         --bios /home/jerome/work/optee_repo/out/bios-qemu/bios.bin
 Starting QEMU... done, guest is booted.
 Loading OP-TEE driver and tee-supplicant... done.
 Running: xtest...
 ##########################################<snip>
 Status: PASS (404 test cases)

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Pascal Brand <pascal.brand@linaro.org>