Currently siginfo files are only written for sstate tasks. In order to be truly
debuggable, its helpful to have the siginfo for intermediate tasks. This
adds that functionality so the extra siginfo files are written out too.
This will be used to add better sstate debugging in future changes.
(From OE-Core rev: 04d108cd16f5ad8f92a62ea537d1330fee712470)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>