Changes the type inference error message so that the position is
proceeded by a space. cmd/go rewrites the output of gc to replace
absolute paths at the beginning of lines and those proceeded by a
space or a tab to relative paths.
Updates testdir to do the same post processing on the output
of tests as cmd/go.
Fixes#68292
Change-Id: Ie109b51143e68f6e7ab4cd19064110db0e609a7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/603097
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
