package/sudo: Enable libxcrypt with glibc, allowing hashed passwords without PAM

Per https://gitlab.com/buildroot.org/buildroot/-/issues/27 , on glibc
builds without PAM, sudo will "fail" all password prompts.

It was found that it's simply checking the entered string against the
raw hash, because 'libcryp' isn't available. On glibc, we need libxcrypt,
so enable it and ensure sudo is built with it.

musl and uclibc do have crypt() functions, so this is not needed.

Relevant code from sudo:
 https://github.com/sudo-project/sudo/blob/v1.9.17p1/plugins/sudoers/auth/passwd.c#L139

Signed-off-by: Nathaniel Roach <nroach44@nroach44.id.au>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/sudo/Config.in

@@ -2,6 +2,7 @@ config BR2_PACKAGE_SUDO
 	bool "sudo"
 	# uses fork()
 	depends on BR2_USE_MMU
+	select BR2_PACKAGE_LIBXCRYPT if BR2_TOOLCHAIN_USES_GLIBC
 	help
 	  Sudo is a program designed to allow a sysadmin to give
 	  limited root privileges to users and log root activity. The

package/sudo/sudo.mk

@@ -37,6 +37,10 @@ else
 SUDO_CONF_OPTS += --without-pam
 endif
 
+ifeq ($(BR2_PACKAGE_LIBXCRYPT),y)
+SUDO_DEPENDENCIES += libxcrypt
+endif
+
 ifeq ($(BR2_PACKAGE_ZLIB),y)
 SUDO_CONF_OPTS += --enable-zlib
 SUDO_DEPENDENCIES += zlib