doc: added a description for the new UseHostEnvVar section in the exa…

…mple file.

rqd/rqd.example.conf

@@ -13,6 +13,9 @@ CHECK_INTERVAL_LOCKED = 60
 # Seconds of idle time required before nimby unlocks.
 MINIMUM_IDLE = 900
 
+# This section tells RQD which env var it should copy from the worker machine to the job's environment.
+# For instance you could need to copy PIXAR_LICENSE_FILE if you launch a renderman job.
+# Note: environment variables will be copied from the machine executing the job, not the sender !
 [UseHostEnvVar]
 # SYSTEMDRIVE is mandatory to allow maya to run in batch via RQD's virtualenv
 SYSTEMDRIVE