compiler: export the type "any" as a builtin

Otherwise we can't tell the difference between builtin type "any" and
a locally defined type "any".

This will require updates to the gccgo export data parsers in the main
Go repo and the x/tools repo.  These updates are https://go.dev/cl/537195
and https://go.dev/cl/537215.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/536715