dashboard: add 'longtest' SlowBot alias

Change-Id: I83cda2cf521b537f4c879d39b473d48faab53965
Reviewed-on: https://go-review.googlesource.com/c/build/+/205858
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index cd5914d..2ba02d6 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -65,6 +65,7 @@
 	"linux-ppc64":    "linux-ppc64-buildlet",
 	"linux-ppc64le":  "linux-ppc64le-buildlet",
 	"linux-s390x":    "linux-s390x-ibm",
+	"longtest":       "linux-amd64-longtest",
 	"mac":            "darwin-amd64-10_14",
 	"macos":          "darwin-amd64-10_14",
 	"mips":           "linux-mips-rtrk",