Trying to install 4.4.0-rc7.powerpc64 I got:
dpkg: error processing package linux-headers-4.4.0-rc-powerpc64 (--install):
dependency problems - leaving unconfigured
Setting up linux-image-4.4.0-rc7-powerpc64 (2) ...
Hmm. There is a symbollic link /lib/modules/4.4.0-rc-powerpc64/build
However, I can not read it: No such file or directory