shadow: fix the behavior of su

In systems where bash is not installed and /bin/sh is provided by
busybox. Commands like `su -l -c '/home/root/test' xuser' would fail
complaining the the 'su' applet could not be found.

This patch references the old version of shadow to keep the behaviour
the way it was in old version so that we would avoid the problem mentioned
above.

(From OE-Core rev: ab0115d1b8a0cb0b25bdb14fd2a3e6c6bb9a44f8)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/shadow/files/0001-su.c-fix-to-exec-command-correctly.patch

@@ -0,0 +1,25 @@
+Upstream-Status: Pending
+
+Subject: su.c: fix to exec command correctly
+
+Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
+---
+ src/su.c |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/su.c b/src/su.c
+index 3704217..bc4f2ac 100644
+--- a/src/su.c
++++ b/src/su.c
+@@ -1156,7 +1156,7 @@ int main (int argc, char **argv)
+ 		 * Use the shell and create an argv
+ 		 * with the rest of the command line included.
+ 		 */
+-		argv[-1] = cp;
++		argv[-1] = shellstr;
+ 		execve_shell (shellstr, &argv[-1], environ);
+ 		err = errno;
+ 		(void) fprintf (stderr,
+-- 
+1.7.9.5
+

meta/recipes-extended/shadow/shadow.inc

@@ -14,6 +14,7 @@ SRC_URI = "http://pkg-shadow.alioth.debian.org/releases/${BPN}-${PV}.tar.xz \
            file://shadow-4.1.3-dots-in-usernames.patch \
            file://usermod-fix-compilation-failure-with-subids-disabled.patch \
            file://fix-installation-failure-with-subids-disabled.patch \
+           file://0001-su.c-fix-to-exec-command-correctly.patch \
            ${@bb.utils.contains('PACKAGECONFIG', 'pam', '${PAM_SRC_URI}', '', d)} \
            "