populate_sdk_ext.bbclass : Show logfile in case the SDK EXT installation failed
To avoid lots of output in the SDK EXT installation phase, system redirects
it to a logfile ($target_sdk_dir/preparing_build_system.log) but in case of error,
the contents should be shown so debugging could be faster.
[YOCTO #9576]
Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
