Add ppc64le architecture

This commit adds PowerPC64 Little Endian atchitecture

Signed-off-by: Dinar Valeev <dvaleev@suse.com>
parse sourcemedium/debugmedium for kiwi product builds
Merge branch 'master' of https://github.com/openSUSE/obs-build into ppc64le
Use BUILD_ARCH instead to check ppc endianes

Build workers are BigEndian, so we can't rely on uname output. Let use
BUILD_ARCH instead.

Signed-off-by: Dinar Valeev <dvaleev@suse.com>