Revert "Rename F_{None,Text,Append} to OF_{None,Text,Append}. NFC"

This reverts commit 58c814614d2ac69bcf79b09543505fac80ada4e6.
Fixes build breakage using LLVM<7.

llvm-svn: 367893

Author: jvesely

libclc/utils/prepare-builtins.cpp

@@ -95,10 +95,10 @@ int main(int argc, char **argv) {
   std::error_code EC;
 #if HAVE_LLVM >= 0x0600
   std::unique_ptr<ToolOutputFile> Out(
-      new ToolOutputFile(OutputFilename, EC, sys::fs::OF_None));
+      new ToolOutputFile(OutputFilename, EC, sys::fs::F_None));
 #else
   std::unique_ptr<tool_output_file> Out(
-      new tool_output_file(OutputFilename, EC, sys::fs::OF_None));
+      new tool_output_file(OutputFilename, EC, sys::fs::F_None));
 #endif
   if (EC) {
     errs() << EC.message() << '\n';