releasing: List some lib paths to set for local libinput

These always bite me, so while probably uncommon may as well document
them...

releasing.txt

@@ -22,6 +22,14 @@ To make a release of Weston and/or Wayland, follow these steps.
 
       export DISTCHECK_CONFIGURE_FLAGS="--with-xserver-path=<your-Xwayland-path>"
 
+	  If you're using a locally installed libinput or other dependency
+	  libraries, you'll likely need to set a few other environment
+	  variables:
+
+	  export WLD="<path-to-your-local-installation>"
+	  export LD_LIBRARY_PATH=$WLD/lib
+	  export PKG_CONFIG_PATH=$WLD/lib/pkgconfig:$WLD/share/pkgconfig/
+
   3.  Run the release.sh script to generate the tarballs, sign and
       upload them, and generate a release announcement template.
       This script can be obtained from X.org's modular package: