godoc: use ARMv6 as the label for arm6 builds.
godoc: use ARMv6 as the label for arm6 builds.

Change-Id: I53c51fb772f23ab3f035b8e50bf017335d01e1c4
Reviewed-on: https://go-review.googlesource.com/18019
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Dave Cheney <bfcdf3e6ca6cef45543bfbb57509c92aec9a39fb@cheney.net>

golang/tools,syreclabs/go-tools,cmars/tools,golang/tools,cmars/tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,cmars/tools,golang/tools,golang/tools,cmars/tools,syreclabs/go-tools,golang/tools