Add a wrapper for open.

This centralizes the handling of O_BINARY and opens the way for hiding more
differences (like how open behaves with directories).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186447 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/ToolOutputFile.h

@@ -47,7 +47,7 @@ public:
   /// tool_output_file - This constructor's arguments are passed to
   /// to raw_fd_ostream's constructor.
   tool_output_file(const char *filename, std::string &ErrorInfo,
-                   unsigned Flags = 0);
+                   sys::fs::OpenFlags Flags = sys::fs::F_None);
 
   tool_output_file(const char *Filename, int FD);