gc: line comments may end in EOF

R=ken2
CC=golang-dev
https://golang.org/cl/2907041

src/cmd/gc/lex.c

@@ -728,14 +728,10 @@ l0:
 		if(c1 == '/') {
 			c = getlinepragma();
 			for(;;) {
-				if(c == '\n') {
+				if(c == '\n' || c == EOF) {
 					ungetc(c);
 					goto l0;
 				}
-				if(c == EOF) {
-					yyerror("eof in comment");
-					errorexit();
-				}
 				c = getr();
 			}
 		}

test/eof1.go

+// $G $D/$F.go
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// No newline at the end of this comment.
\ No newline at end of file