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/raw_ostream.cpp

@@ -454,6 +454,10 @@ raw_ostream &raw_fd_ostream::resetColor() {
   return *this;
 }
 
+bool raw_fd_ostream::is_displayed() const {
+  return sys::Process::FileDescriptorIsDisplayed(FD);
+}
+
 //===----------------------------------------------------------------------===//
 //  raw_stdout/err_ostream
 //===----------------------------------------------------------------------===//