cmd/updatestd: fix working dir of GOWORK check
cmd/updatestd: fix working dir of GOWORK check

Fix for CL 396235.

Change-Id: I486992b21c16924e1ab877b47b32db36ba8b4f3f
Reviewed-on: https://go-review.googlesource.com/c/build/+/396438
Trust: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
Run-TryBot: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/build,golang/build,golang/build,golang/build