tcp-wrappers: drop libnsl2 build dependency

The only libnsl2 function which is used by tcp-wrappers is
'yp_get_default_domain()'.  When USE_GETDOMAIN is set, this is
implemented as a simple wrapper around getdomainname() so that libnsl2
is not used at all.

We added a patch which does '#include <rpcsvc/ypclnt.h>' to avoid
implicit forward declaration.  By conditionalizing this, the libnsl2
dependency can be dropped completely.

(From OE-Core rev: b013f6ce40d315c894064cf9fa77d9c7a9dad2b0)

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/tcp-wrappers/tcp-wrappers-7.6/0001-Fix-implicit-function-declaration-warnings.patch

@@ -20,11 +20,16 @@ diff --git a/hosts_access.c b/hosts_access.c
 index 0133e5e..58697ea 100644
 --- a/hosts_access.c
 +++ b/hosts_access.c
-@@ -33,6 +33,7 @@ static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
+@@ -33,6 +33,12 @@ static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
  #endif
  #include <netinet/in.h>
  #include <arpa/inet.h>
-+#include <rpcsvc/ypclnt.h>
++#ifdef USE_GETDOMAIN
++/* defined in workarounds.c */
++extern int     yp_get_default_domain(char **ptr);
++#else
++#  include <rpcsvc/ypclnt.h>
++#endif	/* USE_GETDOMAIN */
  #include <stdio.h>
  #include <stdlib.h>
  #include <syslog.h>

meta/recipes-extended/tcp-wrappers/tcp-wrappers_7.6.bb

@@ -7,8 +7,6 @@ SECTION = "console/network"
 LICENSE = "BSD-1-Clause"
 LIC_FILES_CHKSUM = "file://DISCLAIMER;md5=071bd69cb78b18888ea5e3da5c3127fa"
 
-DEPENDS += "libnsl2"
-
 PACKAGES = "${PN}-dbg libwrap libwrap-doc libwrap-dev libwrap-staticdev ${PN} ${PN}-doc"
 FILES:libwrap = "${base_libdir}/lib*${SOLIBS}"
 FILES:libwrap-doc = "${mandir}/man3 ${mandir}/man5"