buildroot

support/test-pkg: calculate toolchain name only once

The toolchain name was calculated in main() for reporting to the user,
and again in build_one() for creating the build directory. Calculate
it only once, in main(), and pass the build directory as an argument
to build_one().

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>