build: increase Plan 9 timeout for runtime multi-CPU test, add temporary -v

This isn't the final answer, but it will give us a clue about what's
going on.

Update #9491

Change-Id: I997f6004eb97e86a4a89a8caabaf58cfdf92a8f0
Reviewed-on: https://go-review.googlesource.com/2510Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/run.rc

@@ -34,8 +34,12 @@ echo
 
 # We set GOMAXPROCS=2 in addition to -cpu=1,2,4 in order to test runtime bootstrap code,
 # creation of first goroutines and first garbage collections in the parallel setting.
+# TODO(bradfitz,0intro): make this not be 15 minutes once Plan 9 runs quickly on GCE.
+# Linux does 63 seconds on GCE, but Plan 9 was failing with 8 minutes.
+# See issue 8393 and 9491.
+# TODO(bradfitz,0intro): remove -v once we see some a successful build.
 echo '# GOMAXPROCS=2 runtime -cpu=1,2,4'
-GOMAXPROCS=2 go test runtime -short -timeout 480s -cpu 1,2,4
+GOMAXPROCS=2 go test runtime -v -short -timeout 15m -cpu 1,2,4
 echo
 
 echo '# sync -cpu=10'