It turns out we have quite a number of Makefiles out there without a
clean target. Rather than have all cases code an empty do_configure, add
a CLEANBROKEN variable which when set to "1" will disable the attempt to
"make clean".
This patch also adjusts various recipes which either have this problem
fixed, or have been reported to have make clean failures.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
