package/samba4: needs iconv.h

samba4 needs iconv.h since bump to version 4.15.3 in commit
d33ad03e75b89feb97a7edeba3156fa2ac417b06 and
https://gitlab.com/samba-team/samba/-/commit/fc51b38ed8b7ff239db82d4d2d52f6332910ca97:

../../source3/lib/netapi/examples/common.c:13:10: fatal error: iconv.h: No such file or directory
   13 | #include <iconv.h>
      |          ^~~~~~~~~

Strangely enough, there is no autobuilder failures.

Fixes:
 - https://bugs.buildroot.org/show_bug.cgi?id=14821

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 6a1331ba01b146f4c3a29e0d604e92cf676a46f8)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/samba4/Config.in

@@ -16,6 +16,7 @@ config BR2_PACKAGE_SAMBA4
 	select BR2_PACKAGE_CMOCKA
 	select BR2_PACKAGE_E2FSPROGS
 	select BR2_PACKAGE_GNUTLS
+	select BR2_PACKAGE_LIBICONV if !BR2_ENABLE_LOCALE
 	select BR2_PACKAGE_LIBTIRPC if !BR2_TOOLCHAIN_HAS_NATIVE_RPC
 	select BR2_PACKAGE_POPT
 	select BR2_PACKAGE_ZLIB

package/samba4/samba4.mk

@@ -39,6 +39,11 @@ else
 SAMBA4_CONF_OPTS += --disable-python
 endif
 
+ifeq ($(BR2_PACKAGE_LIBICONV),y)
+SAMBA4_DEPENDENCIES += libiconv
+SAMBA4_LDFLAGS += -liconv
+endif
+
 ifeq ($(BR2_PACKAGE_LIBTIRPC),y)
 SAMBA4_CFLAGS += `$(PKG_CONFIG_HOST_BINARY) --cflags libtirpc`
 SAMBA4_LDFLAGS += `$(PKG_CONFIG_HOST_BINARY) --libs libtirpc`