cmd/compile: enable -d=checkptr even on windows

CL 201783 enable -d=checkptr when -race or -msan is specified
everywhere but windows.

But, now that all unsafe pointer conversions in the standard
library are fixed, enable -d=checkptr even on windows.

Updates #34964
Updates #34972

Change-Id: Id912fa83b0d5b46c6f1c134c742fd94d2d185835
Reviewed-on: https://go-review.googlesource.com/c/go/+/227003
Run-TryBot: Alex Brainman <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: alexbrainman

src/cmd/compile/internal/gc/main.go

@@ -379,9 +379,8 @@ func Main(archInit func(*Arch)) {
 	if flag_race && flag_msan {
 		log.Fatal("cannot use both -race and -msan")
 	}
-	if (flag_race || flag_msan) && objabi.GOOS != "windows" {
-		// -race and -msan imply -d=checkptr for now (except on windows).
-		// TODO(mdempsky): Re-evaluate before Go 1.14. See #34964.
+	if flag_race || flag_msan {
+		// -race and -msan imply -d=checkptr for now.
 		Debug_checkptr = 1
 	}
 	if ispkgin(omit_pkgs) {