cmd/compile: replace os.MkdirTemp with T.TempDir

cmd/compile: replace os.MkdirTemp with T.TempDir

Updates #45402

Change-Id: Ieffd1c8b0b5e4e63024b5be2e1f910fb4411eb94
GitHub-Last-Rev: fa7418c8eb977b7214311e774f9df7a1220a3dfd
GitHub-Pull-Request: golang/go#57940
Reviewed-on: https://go-review.googlesource.com/c/go/+/462896
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>