[kpatch] missing removal of changed_objs

[Martin Carroll]

Hi Josh, thanks for the fast reply!
> When the original kernel is built, TEMPDIR hasn't been exported yet.
I already had TEMPDIR set (and exported) in my own shell environment.  
Shell scripts should never assume that they "own" an environment 
variable.  The user's environment on entering the script can be 
anything.  If you want to bypass the special logic in kpatch-gcc using 
the "look for an empty environment variable" trick, then kpatch-build 
must explicitly make that environment variable empty before invoking the 
original make.

Martin Carroll