Support for PREBUILT_ILLUMOS, and optional /tmp/debug.$$ output.

@@ -6,9 +6,14 @@
 # the top level of your checkout and publish there instead
 # of the URI specified above.
 #
 #PKGSRVR=file:///$MYDIR/../tmp.repo/
 
+# Uncommenting this line will use a pre-built illumos-omnios, instead of having
+# us build it.  NOTE: A build of illumos-omnios can be launched concurrently in
+# conjunction with setting this variable. See functions.sh:wait_for_prebuilt().
+#PREBUILT_ILLUMOS=$HOME/build/prebuild
+
 # These two should be uncommented and set to specific git changeset IDs
 # if illumos-kvm and illumos-kvm-cmd get too far ahead of illumos-{gate,omnios}.
 #KVM_ROLLBACK=a8ea37e8deb99265682c66c23f787f704e77fb91
 #KVM_CMD_ROLLBACK=1c6181be55d1cadc4426069960688307a6083131