net/netatalk3: Use iconv:wchar_t to fix build when DBUS is disabled

This mirrors what glib20 uses for iconv, and will ensure that we bring
in converters/libiconv in all cases.  Not bumping PORTREVISION as the
dependency list doesn't change in the default case.

PR:		281096

net/netatalk3/Makefile

@@ -14,7 +14,7 @@ LICENSE=	GPLv2
 LIB_DEPENDS=	libgcrypt.so:security/libgcrypt \
 		libevent.so:devel/libevent
 
-USES=		bdb:18 cpe gettext iconv meson perl5 pkgconfig shebangfix ssl tar:xz
+USES=		bdb:18 cpe gettext iconv:wchar_t meson perl5 pkgconfig shebangfix ssl tar:xz
 USE_LDCONFIG=	yes
 USE_RC_SUBR=	netatalk
 #INSTALL_TARGET=install-strip