selinux: don't use make's grouped targets feature yet

The Linux Kernel currently only requires make v3.82 while the grouped
target functionality requires make v4.3.  Removed the grouped target
introduced in 4ce1f69 ("selinux: ensure av_permissions.h is
built when needed") as well as the multiple header file targets in
the make rule.  This effectively reverts the problem commit.

We will revisit this change when make >= 4.3 is required by the rest
of the kernel.

Cc: stable@vger.kernel.org
Fixes: 4ce1f69 ("selinux: ensure av_permissions.h is built when needed")
Reported-by: Erwan Velu <e.velu@criteo.com>
Reported-by: Luiz Capitulino <luizcap@amazon.com>
Tested-by: Luiz Capitulino <luizcap@amazon.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/Makefile

@@ -26,5 +26,9 @@ quiet_cmd_flask = GEN     $(obj)/flask.h $(obj)/av_permissions.h
       cmd_flask = $< $(obj)/flask.h $(obj)/av_permissions.h
 
 targets += flask.h av_permissions.h
-$(obj)/flask.h $(obj)/av_permissions.h &: scripts/selinux/genheaders/genheaders FORCE
+# once make >= 4.3 is required, we can use grouped targets in the rule below,
+# which basically involves adding both headers and a '&' before the colon, see
+# the example below:
+#   $(obj)/flask.h $(obj)/av_permissions.h &: scripts/selinux/...
+$(obj)/flask.h: scripts/selinux/genheaders/genheaders FORCE
 	$(call if_changed,flask)