Use LLVM for file / directory enumeration.

FileSpec::EnumerateDirectory has a bunch of platform-specific
gunk in it for posix and non-posix platforms. We can get rid
of all this by using LLVM's easy-to-use directory iterators.

Differential Revision: https://reviews.llvm.org/D30807

llvm-svn: 297598
diff --git a/lldb/source/Commands/CommandCompletions.cpp b/lldb/source/Commands/CommandCompletions.cpp
index 16e4de0..34b7d78 100644
--- a/lldb/source/Commands/CommandCompletions.cpp
+++ b/lldb/source/Commands/CommandCompletions.cpp
@@ -195,7 +195,7 @@
     // We have a match.
 
     fs::file_status st;
-    if (EC = Entry.status(st))
+    if ((EC = Entry.status(st)))
       continue;
 
     // If it's a symlink, then we treat it as a directory as long as the target