test: add barebones /etc/{passwd,group} and an ld.so.conf

Finit now requires being able to query at least for the root user and
group before starting any services.

Also, add support for using libraries installed in /usr/local

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/skel/etc/passwd

@@ -0,0 +1,5 @@
+root:x:0:0:root:/root:/bin/sh
+daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
+bin:x:2:2:bin:/bin:/usr/sbin/nologin
+sys:x:3:3:sys:/dev:/usr/sbin/nologin
+nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin