util-linux: linux-pam is needed for su

With linux-pam, the configure script bails out with:

configure: error: su selected, but required PAM header file not available

Fixes:
http://autobuild.buildroot.net/results/338/3381a49d17aa0d4b9711cbb36a5d7b563a8ae08f/
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/util-linux/Config.in

@@ -330,10 +330,18 @@ config BR2_PACKAGE_UTIL_LINUX_SETTERM
 
 config BR2_PACKAGE_UTIL_LINUX_SU
 	bool "su"
-	depends on BR2_USE_MMU # fork()
+	depends on (BR2_ENABLE_LOCALE && BR2_USE_WCHAR) # linux-pam
+	depends on !BR2_STATIC_LIBS
+	depends on !BR2_TOOLCHAIN_USES_MUSL # linux-pam
+	depends on BR2_USE_MMU # fork(), linux-pam
+	select BR2_PACKAGE_LINUX_PAM
 	help
 	  Run a command with substitute user and group ID
 
+comment "su needs a uClibc or glibc toolchain w/ wchar, locale, dynamic library"
+	depends on !(BR2_ENABLE_LOCALE && BR2_USE_WCHAR) \
+		|| BR2_STATIC_LIBS || BR2_TOOLCHAIN_USES_MUSL
+
 config BR2_PACKAGE_UTIL_LINUX_SULOGIN
 	bool "sulogin"
 	depends on BR2_USE_MMU # fork()