Check for export dynamic symbol options when doing symbol resolution in plugins.

2017-09-20  Teresa Johnson  <tejohnson@google.com>
	* plugin.cc (is_visible_from_outside): Check for export dynamic symbol
        option and list.
	* testsuite/Makefile.am (plugin_test_12): New test.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/export_dynamic_plugin.cc: New test source.
	* testsuite/plugin_test_12.sh: New test script.

gold/testsuite/export_dynamic_plugin.cc

@@ -0,0 +1,29 @@
+/* export_dynamic_plugin.c -- a test case for gold
+
+   Copyright (C) 2017 onwards Free Software Foundation, Inc.
+   Written by Teresa Johnson <tejohnson@google.com>.
+
+   This file is part of gold.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+   MA 02110-1301, USA.  */
+
+int foo(void) {
+  return 0;
+}
+
+int main(void) {
+  return 0;
+}