Some TARGET_* flags are being exported in bitbake.conf currently, so
they are impacting all the tasks of a cross recipe even they are not
in use at all.
This can lead a lot of churn when the cross sysroot are shared by
machines while they have defined different TARGET_* flags.
And sometimes it even causes "Taskhash mismatch" errors.
Fix it by overriding with BUILD_* flags.
Signed-off-by: Ming Liu <peter.x.liu@external.atlascopco.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
