When renaming the libxenguest sources to xg_*.c there was an omission
in the Makefile when setting the zlib related define for the related
sources. Fix that.
Fixes: e3dd624e48 ("tools/libxc: move libxenguest to tools/libs/guest")
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>