Kernels which use tools/objtool can now fail when building external modules
due to objtool being missing, the generated files can also cause problems
for kernel-devsrc.
Ensure objtool is generated in make-mod-scripts by also calling
"make prepare".
For devsrc, delete the generated binaries since they'd be native
binaries and unsuitable for the target.
The oeqa kernel module tests also need to have the additional "make prepare"
step added.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
