scripts/contrib: add build time regression test script
test_build_time.sh is a bash script intended to be used in conjunction
with "git bisect run" in order to find regressions in build time, however
it can also be used independently. It cleans out the build output
directories, runs a specified worker script (an example is
test_build_time_worker.sh) under TIME(1), logs the results, and returns
a value telling "git bisect run" whether the build time is good (under
the specified threshold) or bad (over it).
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
