package/samba4: needs libxcrypt

Since the bump of Samba to version 4.21.4 in commit
716461af94, <crypt.h> is needed, due to
upstream comit 0dccda38f27b3bbda5d2a4de588a333ff554651a. Since
<crypt.h> is no longer provided by glibc, a dependency on libxcrypt is
needed, to avoid the following build failure:

../../lib/util/util_crypt.c:5:10: fatal error: crypt.h: No such file or directory
    5 | #include <crypt.h>
      |          ^~~~~~~~~
compilation terminated.

This has not been detected by the autobuilders, presumably because a
lot of glibc configurations end up having libxcrypt selected by other
packages, but the issue is reproducible by building:

BR2_arm=y
BR2_cortex_a9=y
BR2_ARM_ENABLE_VFP=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
BR2_PACKAGE_SAMBA4=y

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 6c3f01fde1)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

package/samba4/Config.in

@@ -17,6 +17,7 @@ config BR2_PACKAGE_SAMBA4
 	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_LIBXCRYPT if BR2_TOOLCHAIN_USES_GLIBC
 	select BR2_PACKAGE_POPT
 	select BR2_PACKAGE_ZLIB
 	help

package/samba4/samba4.mk

@@ -22,6 +22,7 @@ SAMBA4_DEPENDENCIES = \
 	$(if $(BR2_PACKAGE_LIBCAP),libcap) \
 	$(if $(BR2_PACKAGE_LIBGLIB2),libglib2) \
 	$(if $(BR2_PACKAGE_READLINE),readline) \
+	$(if $(BR2_PACKAGE_LIBXCRYPT),libxcrypt) \
 	$(TARGET_NLS_DEPENDENCIES)
 SAMBA4_CFLAGS = $(TARGET_CFLAGS)
 SAMBA4_LDFLAGS = $(TARGET_LDFLAGS) $(TARGET_NLS_LIBS)