add b64_ntop checking and fallback for nc(1)

m4/check-libc.m4

@@ -2,7 +2,8 @@ AC_DEFUN([CHECK_LIBC_COMPAT], [
 # Check for libc headers
 AC_CHECK_HEADERS([err.h readpassphrase.h])
 # Check for general libc functions
-AC_CHECK_FUNCS([accept4 asprintf inet_pton memmem poll readpassphrase reallocarray])
+AC_CHECK_FUNCS([accept4 asprintf inet_pton memmem poll])
+AC_CHECK_FUNCS([readpassphrase reallocarray])
 AC_CHECK_FUNCS([strlcat strlcpy strndup strnlen strsep strtonum])
 AM_CONDITIONAL([HAVE_ACCEPT4], [test "x$ac_cv_func_accept4" = xyes])
 AM_CONDITIONAL([HAVE_ASPRINTF], [test "x$ac_cv_func_asprintf" = xyes])
@@ -19,6 +20,25 @@ AM_CONDITIONAL([HAVE_STRSEP], [test "x$ac_cv_func_strsep" = xyes])
 AM_CONDITIONAL([HAVE_STRTONUM], [test "x$ac_cv_func_strtonum" = xyes])
 ])
 
+AC_DEFUN([CHECK_B64_NTOP], [
+AC_SEARCH_LIBS([b64_ntop],[resolv])
+AC_SEARCH_LIBS([__b64_ntop],[resolv])
+AC_CACHE_CHECK([for b64_ntop], ac_cv_have_b64_ntop_arg, [
+	AC_LINK_IFELSE([AC_LANG_PROGRAM([[
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <resolv.h>
+		]], [[ b64_ntop(NULL, 0, NULL, 0); ]])],
+	[ ac_cv_have_b64_ntop_arg="yes" ],
+	[ ac_cv_have_b64_ntop_arg="no"
+	])
+])
+AM_CONDITIONAL([HAVE_B64_NTOP], [test "x$ac_cv_func_b64_ntop" = xyes])
+])
+
+
 AC_DEFUN([CHECK_LIBC_CRYPTO_COMPAT], [
 # Check crypto-related libc functions
 AC_CHECK_FUNCS([arc4random_buf explicit_bzero getauxval getentropy])

m4/check-os-options.m4

@@ -17,7 +17,6 @@ case $host_os in
 		BUILD_NC=yes
 		HOST_OS=darwin
 		HOST_ABI=macosx
-		AC_SUBST([PROG_LDADD], ['-lresolv'])
 		;;
 	*freebsd*)
 		HOST_OS=freebsd
@@ -39,7 +38,6 @@ case $host_os in
 		HOST_OS=linux
 		HOST_ABI=elf
 		CPPFLAGS="$CPPFLAGS -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_SOURCE -D_GNU_SOURCE"
-		AC_SUBST([PROG_LDADD], ['-lresolv'])
 		;;
 	*netbsd*)
 		HOST_OS=netbsd