[test] Use correct macro in FileCollectorTest.cpp

This test was supposed to be skipped on Windows but was using the wrong
macro name.

llvm-svn: 352556

lldb/unittests/Utility/FileCollectorTest.cpp

@@ -151,7 +151,7 @@ TEST(FileCollectorTest, CopyFiles) {
   EXPECT_FALSE(ec);
 }
 
-#ifndef WINDOWS
+#ifndef _WIN32
 TEST(FileCollectorTest, Symlinks) {
   // Root where the original files live.
   ScopedDir file_root("file_root", true);