sstatesig: include native/cross/nativesdk deps in target signatures

sstatesig: include native/cross/nativesdk deps in target signatures

* I don't have any real evidence or good statistics for this, but when
  comparing signature dumps from my big bitbake world builds I usually
  see a lot of rebuilds caused by changes in .bbclasses and only very
  rare would be the case where oe-core upgrade brings changes in -native
  recipes and no change in .bbclasses used from target recipes
* changing the default to include them shouldn't cause significant
  increase in rebuilds and sstate reuse a bit safer
* people working on toolchain (e.g. using gcc from AUTOREV) can easily
  extend sstate_rundepfilter to ignore them again (it's easier than
  removing existing filter), example how add own signature handler in
  your layer is here:
  https://github.com/openwebos/meta-webos/commit/9ac3a7c803e7793b3274e4998f167b6278db8042

(From OE-Core rev: 336a7897e39b9e42dcfcba9e2520ea96b0c6a8d6)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>