fake_id0: Make sudo work under PRoot.

The program sudo changes its effective uid before checking that the
owner of /etc/sudoers is root.  As a consequence, the faked owner of
this file -- and of all other files owned by the real user -- is the
new effective uid.  Sadly, this makes sudo aborts because the owner of
/etc/sudoers is not root.  A workaround is to use the save uid as the
faked owner of all files owned by the real user.

This was tested with "makepkg -i" on a Archi Linux guest rootfs.

Ref.: fsquillace/junest#59

src/extension/fake_id0/fake_id0.c

@@ -654,10 +654,10 @@ static int handle_sysexit_end(Tracee *tracee, Config *config)
 		/* Override only if the file is owned by the current user.
 		 * Errors are not fatal here.  */
 		if (uid == getuid())
-			poke_uint32(tracee, address + offsetof_stat_uid(tracee), config->ruid);
+			poke_uint32(tracee, address + offsetof_stat_uid(tracee), config->suid);
 
 		if (gid == getgid())
-			poke_uint32(tracee, address + offsetof_stat_gid(tracee), config->rgid);
+			poke_uint32(tracee, address + offsetof_stat_gid(tracee), config->sgid);
 
 		return 0;
 	}