dbus: several fixes

- disable the tests as (they warn) they make the library insecure
- add libX11 (was missing something)
- dirty hack around the "incomplete struct ucred" problem
	(feel free to find a better solution, I tried almost 1h)

pkgs/development/libraries/dbus/default.nix

@@ -8,9 +8,12 @@ let
     sha256 = "fc1370ef38abeeb13f55c905ec002e60705fb0bfde3b8d21c8d6eb8056c11bac";
   };
 
-  patches = [ ./ignore-missing-includedirs.patch ./implement-getgrouplist.patch ];
+  patches = [
+    ./ignore-missing-includedirs.patch ./implement-getgrouplist.patch
+    ./ucred-dirty-hack.patch
+  ];
 
-  configureFlags = "--enable-embedded-tests --localstatedir=/var --sysconfdir=/etc --with-session-socket-dir=/tmp";
+  configureFlags = "--localstatedir=/var --sysconfdir=/etc --with-session-socket-dir=/tmp";
 
 in rec {
 
@@ -19,7 +22,7 @@ in rec {
 
     nativeBuildInputs = [ pkgconfig ];
 
-    buildInputs = [ expat ];
+    buildInputs = [ expat libX11 ];
 
     # FIXME: dbus has optional systemd integration when checking
     # at_console policies.  How to enable this without introducing a

pkgs/development/libraries/dbus/ucred-dirty-hack.patch

@@ -0,0 +1,18 @@
+diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
+index b4ecc96..267984a 100644
+--- a/dbus/dbus-sysdeps-unix.c
++++ b/dbus/dbus-sysdeps-unix.c
+@@ -1635,6 +1635,13 @@ write_credentials_byte (int             server_fd,
+     }
+ }
+ 
++struct ucred
++{
++  pid_t pid;			/* PID of sending process.  */
++  uid_t uid;			/* UID of sending process.  */
++  gid_t gid;			/* GID of sending process.  */
++};
++
+ /**
+  * Reads a single byte which must be nul (an error occurs otherwise),
+  * and reads unix credentials if available. Clears the credentials