Change test fixture from symlink to regular file

The only test using this is test/simple/test-fs-chmod.js, and it was
treating a.js and a1.js as two separate files, resulting in a race
condition.  (Interestingly enough, it was *not* using the symlink file to
test lchmod, which uses a different temp file.)

test/fixtures/a1.js

@@ -1 +0,0 @@
-a.js

test/fixtures/a1.js

@@ -0,0 +1,46 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var c = require('./b/c');
+
+console.error('load fixtures/a.js');
+
+var string = 'A';
+
+exports.SomeClass = c.SomeClass;
+
+exports.A = function() {
+  return string;
+};
+
+exports.C = function() {
+  return c.C();
+};
+
+exports.D = function() {
+  return c.D();
+};
+
+exports.number = 42;
+
+process.on('exit', function() {
+  string = 'A done';
+});