livepatch: use basename to perform object file matching

livepatch: use basename to perform object file matching

The changes in the Xen build logic has resulted in the compiler and
objcopy being called from xen/ instead of relative to each object
directory. This requires using basename so that the directory is not
taken into account when checking against the list of files to be
explicitly ignored.

Also adjust the paths used to store the differing object files, as
with the current logic the resulting path will be wrong when using
newer Xen versions, changed_objs would end containing entries like:

xen/arch/x86/hvm/vmx/arch/x86/hvm/vmx/vmx.o

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Bjoern Doebel <doebel@amazon.de>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>