plymouth: fix path to systemd-tty-ask-password-agent

In pre recipe specific sysroot times AC_PATH_PROG detected host's
systemd-tty-ask-password-agent. In my case that path was wrong and
systemd-ask-password-plymouth.service failed silently.
Now with recipe specific sysroot and no link in PATH to buildhost,
SYSTEMD_ASK_PASSWORD_AGENT remains empty and that causes:

| systemd[1]: /lib/systemd/system/systemd-ask-password-plymouth.service:12: Executable path is not absolute, ignoring: --watch --plymouth
| systemd[1]: systemd-ask-password-plymouth.service: Service lacks both ExecStart= and ExecStop= setting. Refusing.

For both environments this patch fixes log-off from X-session to
display-manager. Before this patch screen went dark and it seemed that X-server
was restarted.

Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-core/plymouth/files/0001-Make-full-path-to-systemd-tty-ask-password-agent-con.patch

@@ -0,0 +1,34 @@
+From 746c690f57b52e6fe21cc2a11b5bb71d25af3128 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Andreas=20M=C3=BCller?= <schnitzeltony@gmail.com>
+Date: Wed, 13 Dec 2017 16:15:57 +0100
+Subject: [PATCH] Make full path to systemd-tty-ask-password-agent configurable
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Upstream-Status: Inappropriate [embedded specific]
+
+Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>
+---
+ configure.ac | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/configure.ac b/configure.ac
+index aad673e..6b37179 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -48,7 +48,10 @@ PLYMOUTH_LIBS="-lm -lrt -ldl"
+ AC_SUBST(PLYMOUTH_CFLAGS)
+ AC_SUBST(PLYMOUTH_LIBS)
+ 
+-AC_PATH_PROG([SYSTEMD_ASK_PASSWORD_AGENT], [systemd-tty-ask-password-agent])
++AC_ARG_WITH(systemd-tty-ask-password-agent, AS_HELP_STRING([--with-systemd-tty-ask-password-agent],[path of systemd-tty-ask-password-agent]),SYSTEMD_ASK_PASSWORD_AGENT=${withval},SYSTEMD_ASK_PASSWORD_AGENT=/bin/systemd-tty-ask-password-agent)
++AC_SUBST(SYSTEMD_ASK_PASSWORD_AGENT)
++
++# checked: UDEVADM is not used
+ AC_PATH_PROG([UDEVADM], [udevadm])
+ 
+ AC_ARG_ENABLE(pango, AS_HELP_STRING([--enable-pango],[enable building with pango, disabled there is no encryption prompts]),enable_pango=$enableval,enable_pango=yes)
+-- 
+2.9.5
+

meta-oe/recipes-core/plymouth/plymouth_0.9.2.bb

@@ -16,13 +16,16 @@ DEPENDS = "libcap libpng cairo dbus udev"
 PROVIDES = "virtual/psplash"
 RPROVIDES_${PN} = "virtual-psplash virtual-psplash-support"
 
-SRC_URI = "http://www.freedesktop.org/software/plymouth/releases/${BPN}-${PV}.tar.bz2"
+SRC_URI = " \
+    http://www.freedesktop.org/software/plymouth/releases/${BPN}-${PV}.tar.bz2 \
+    file://0001-Make-full-path-to-systemd-tty-ask-password-agent-con.patch \
+"
 SRC_URI[md5sum] = "ff420994deb7ea203df678df92e7ab7d"
 SRC_URI[sha256sum] = "2f0ce82042cf9c7eadd2517a1f74c8a85fa8699781d9f294a06eade29fbed57f"
 
 EXTRA_OECONF += " --enable-shared --disable-static --disable-gtk --disable-documentation \
     --with-logo=${LOGO} \
-    ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', '--enable-systemd-integration --with-system-root-install', '', d)} \
+    ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', '--enable-systemd-integration --with-system-root-install --with-systemd-tty-ask-password-agent=${base_bindir}/systemd-tty-ask-password-agent', '', d)} \
 "
 
 PACKAGECONFIG ??= "pango initrd"