Update README for OpenBSD build

README

@@ -37,7 +37,7 @@ In order to build slstatus you need the Xlib header files.
 Installation
 ------------
 Edit config.mk to match your local setup (slstatus is installed into the
-/usr/local namespace by default).
+/usr/local namespace by default). Uncomment OSSLIBS on OpenBSD.
 
 Afterwards enter the following command to build and install slstatus (if
 necessary as root):