classes/populate_sdk_ext.bbclass: handle if local.conf doesn't end with a newline
If there is no newline at the end of local.conf, appending
INHERIT = "uninative" won't work, it will corrupt the line and the
installed eSDK will build things, making the "Preparing build system..."
step take an age.
Fixes [YOCTO #8897].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
