The previous patch made sure a truncated key would be re-generated
but it broke the case that there is no key at all. This code is
handling both cases now. Use quotes as code outside this method
is using them too. Use the -a and not the && operator to work with
the busybox version of [ and ].
The idea is that the basic extension resides inside the the normal
recipe directories. Depending on the version of poky the bbappends
need to be included. Appends applying to all versions will be put
into the shared folder, specific ones into the specific directory.
Once a bbappend can not be shared anymore it needs to be copied.