On Plan 9, the pwd is apparently per-thread not per process. That
means different goroutines saw different current directories, even
changing within a goroutine as they were scheduled.
Instead, track the the process-wide pwd protected by a mutex in the
syscall package and set the current goroutine thread's pwd to the
correct once at critical points.
Fixes#9428
Change-Id: I928e90886355be4a95c2be834f5883e2b50fc0cf
Reviewed-on: https://go-review.googlesource.com/6350
Reviewed-by: David du Colombier <0intro@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
envi needs to be updated during Setenv so the key can be correctly deleted later with Unsetenv.
Update #8849.
LGTM=0intro
R=bradfitz, 0intro
CC=golang-codereviews
https://golang.org/cl/149300046
