iostest.bash: don't build std library twice

Instead, mirror androidtest.bash and build once, then run run.bash.

Change-Id: I174ae30b2a429a62b20bb290a70cb07ed712b1e4
Reviewed-on: https://go-review.googlesource.com/98915Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/iostest.bash

@@ -69,5 +69,5 @@ if [ "$GOIOS_DEV_ID" = "" ]; then
 	eval $(GOOS=$GOHOSTOS GOARCH=$GOHOSTARCH go run ../misc/ios/detect.go)
 fi
 
-# Run standard build and tests.
-./all.bash --no-clean
+# Run standard tests.
+bash run.bash --no-rebuild