tools/intrinsic: Handle CRLF

Fixes cryptic error message:

error calling Sem: src/tint/intrinsics.def:14:1: unexpected '

Change-Id: Ic343e77f6a1976ebdc4952eb590751c34b014be8
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/108143
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

tools/src/tint/intrinsic/lexer/lexer.go

@@ -50,7 +50,7 @@ func (l *lexer) lex() error {
 			return nil
 		case ' ', '\t':
 			l.next()
-		case '\n':
+		case '\r', '\n':
 			l.next()
 		case '@':
 			l.tok(1, tok.Attr)