We source some scripts, but still pass parameters to them, e.g.

	. mk_version_h $@ $(KERNELRELEASE) $(VERSION) ...

This does not work for all kinds of /bin/sh (it does for bash, that's
why I did not notice).

The fix is easy: Just mark the scripts executable and call instead of
source them.

Unfortunately, patch(1) doesn't understand about propagating chmod.
bk does, so changing the tree isn't hard, and we introduce an explicit
chmod a+x executed during the build for propagating this change into
those trees which get "traditionally" patched up.