Previous CLs added symlink evaulation to GOROOT and GOPATH.
Unfortunately that only fixed tests that ran outside GOROOT.

To fix the standard library tests, evaluate symlinks in the current
working directory as well.

Change-Id: Ia406a968235ae4321a1002567520105998582d15
Reviewed-on: https://go-review.googlesource.com/c/164699
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>