deploy: fail the goprev deployment if latestgo fails

In golang/go#59303, we observed (surprisingly) that the goprev
playground deployment proceeded with deploying using tip Go after the
latestgo command failed.

Fix the latestgo invocation to exit with a non-zero exit code when
latestgo fails.

For golang/go#59303

Change-Id: Ie07764b71ce42bddbff6266b0bb8684140d02af4
Reviewed-on: https://go-review.googlesource.com/c/playground/+/480275
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/deploy/deploy_goprev.json b/deploy/deploy_goprev.json
index 660f8a8..a4731cc 100644
--- a/deploy/deploy_goprev.json
+++ b/deploy/deploy_goprev.json
@@ -8,7 +8,7 @@
       "entrypoint": "bash",
       "args": [
         "-c",
-        "go run golang.org/x/playground/cmd/latestgo -prev > /workspace/goversion; echo GO_VERSION=`cat /workspace/goversion`"
+        "go run golang.org/x/playground/cmd/latestgo -prev > /workspace/goversion && echo GO_VERSION=`cat /workspace/goversion`"
       ]
     },
     {