When running bitbake command with Python 3.6.5 always result in
import error causing by the change of distutils module.
This patch replaces the method to search executable in PATH by
"/usr/bin/env <command>".
(Bitbake rev: bd9a1b063633af2936ba1dd87b19202424900151)
Signed-off-by: Tzu Hsiang Lin <t9360341@ntut.org.tw>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>