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

*** 163,172 ****
--- 163,176 ----
          shift
          tobuild=$*
          if [ -z "$tobuild" ] || [ "$tobuild" == "all" ]; then
                  batch_flag="-b"
                  for tgt in "${!fulltargets[@]}"; do
+                         # Uncomment the echo line if you want to see a
+                         # one-package-per-line status of what's building in
+                         # /tmp/debug.<PID>.
+                         # echo "Target = $tgt" >> /tmp/debug.$$
                          build $tgt
                  done
          else
                  for tgt in $tobuild; do
                          build $tgt