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/setup-sysroot.sh

@@ -21,3 +21,6 @@ done
 for conf in 10-hotplug.conf; do
     find "$SYSROOT" -name $conf -delete
 done
+
+# Update dynamic linker cache for /usr/local/lib libraries
+ldconfig -r "$SYSROOT"