ldconfig: add aout deprecation notice

aout support in ldconfig hasn't been required since FreeBSD 2.x.
Anyone still using FreeBSD 2 shared libraries can also use a FreeBSD 2
ldconfig to generate aout ldconfig hints.

Sponsored by:	The FreeBSD Foundation

sbin/ldconfig/ldconfig.8

@@ -29,7 +29,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 6, 2018
+.Dd March 17, 2020
 .Dt LDCONFIG 8
 .Os
 .Sh NAME
@@ -111,6 +111,8 @@ Generate the hints for 32-bit ABI shared libraries
 on 64-bit systems that support running 32-bit binaries.
 .It Fl aout
 Generate the hints for a.out format shared libraries.
+This option is deprecated and is not present in
+.Fx 13 .
 .It Fl elf
 Generate the hints for ELF format shared libraries.
 .It Fl R

sbin/ldconfig/ldconfig.c

@@ -118,6 +118,7 @@ main(int argc, char **argv)
 
 	while (argc > 1) {
 		if (strcmp(argv[1], "-aout") == 0) {
+			warnx("aout support is deprecated");
 			is_aout = 1;
 			argc--;
 			argv++;