cmd/compile: don't call hcrash in Warn

Fixes #31638.

Change-Id: I748f64b48b75241a9db31c9f37555379a841677a
Reviewed-on: https://go-review.googlesource.com/c/go/+/173443
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -159,9 +159,7 @@ func yyerror(format string, args ...interface{}) {
 }
 
 func Warn(fmt_ string, args ...interface{}) {
-	adderr(lineno, fmt_, args...)
-
-	hcrash()
+	Warnl(lineno, fmt_, args...)
 }
 
 func Warnl(line src.XPos, fmt_ string, args ...interface{}) {