cmd/compile: use raw strings to avoid double escapes
Change-Id: I9b24ff7dec0825a8a9d094dfef6553aa605ef47d
GitHub-Last-Rev:
785589211cea172377bb67e895491d8678939600
GitHub-Pull-Request: golang/go#67871
Reviewed-on: https://go-review.googlesource.com/c/go/+/591257
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>