Fix llvm-extract's "writing bitcode to a terminal" warning, which wasn't

working. To support this, add an is_displayed() function to raw_ostream,
and generalize Process::StandardOutIsDisplayed and friends in order to
support it.

Also, call RemoveFileOnSignal before creating a file instead of after, so
that the file isn't left behind if the program is interrupted between when
the file is created and RemoveFileOnSignal is called.

While here, add a -S to llvm-extract and port it to IRReader so that it
supports assembly input.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81568 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/SystemUtils.cpp

@@ -20,8 +20,7 @@ using namespace llvm;
 
 bool llvm::CheckBitcodeOutputToConsole(raw_ostream &stream_to_check,
                                        bool print_warning) {
-  if (&stream_to_check == &outs() &&
-      sys::Process::StandardOutIsDisplayed()) {
+  if (stream_to_check.is_displayed()) {
     if (print_warning) {
       errs() << "WARNING: You're attempting to print out a bitcode file.\n"
              << "This is inadvisable as it may cause display problems. If\n"