go.tools/dashboard: Don't keep unversioned directories in gcc copy.
go.tools/dashboard: Don't keep unversioned directories in gcc copy.

`svn update` would fail if the updated files were in the gcc/libgo or gcc/go/gofrontend because unrevisioned versions of those files had been inserted in the last build of gcc.

R=adg, adg
CC=golang-dev
https://codereview.appspot.com/14299043

bryanxu/go-zh.tools,d0f/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,d0f/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,skyportsystems/go.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,8limbs/gotools,skyportsystems/go.tools,8limbs/gotools,d0f/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,webfd/go-zh.tools,d0f/go-zh.tools,skyportsystems/go.tools,skyportsystems/go.tools