buildroot

pkg-autotools: don't disable dependency tracking if using <pkg>_OVERRIDE_SRCDIR

Include the --disable-dependency-tracking option in <pkg>_CONFIGURE_CMDS
only on the condition that <pkg>_OVERRIDE_SRCDIR is empty. Dependency
tracking is very welcome while developing in order to properly rebuild
when calling make <pkg>-rebuild for instance.

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>