dashboard: add -d=dclstack to ssacheck builder
dashboard: add -d=dclstack to ssacheck builder

Fixes golang/go#18621

Change-Id: I362ab473136cce659fa267d5bfc0a670389e3fc4
Reviewed-on: https://go-review.googlesource.com/38321
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build