add llvm configure flags to enable/disable target OSes/Envs

lib/MC/MCObjectFileInfo.cpp

 //===-- MObjectFileInfo.cpp - Object File Information ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCObjectFileInfo.h"
@@ skipping 497 matching lines @@
   EHFrameSection = 0; // Created on demand.
 
   Triple T(TT);
   Triple::ArchType Arch = T.getArch();
   // FIXME: Checking for Arch here to filter out bogus triples such as
   // cellspu-apple-darwin. Perhaps we should fix in Triple?
   if ((Arch == Triple::x86 || Arch == Triple::x86_64 ||
        Arch == Triple::arm || Arch == Triple::thumb ||
        Arch == Triple::ppc || Arch == Triple::ppc64 ||
        Arch == Triple::UnknownArch) &&
-      (T.isOSDarwin() || T.getEnvironment() == Triple::MachO)) {
+      (T.isOSDarwin() || T.isEnvironmentMachO())) {
     Env = IsMachO;
     InitMachOMCObjectFileInfo(T);
   } else if ((Arch == Triple::x86 || Arch == Triple::x86_64) &&
-             (T.getOS() == Triple::MinGW32 || T.getOS() == Triple::Cygwin ||
-              T.getOS() == Triple::Win32)) {
+             T.isOSWindows()) {
     Env = IsCOFF;
     InitCOFFMCObjectFileInfo(T);
   } else {
     Env = IsELF;
     InitELFMCObjectFileInfo(T);
   }
 }
 
 void MCObjectFileInfo::InitEHFrameSection() {
   if (Env == IsMachO)
@@ skipping 10 matching lines @@
                          ELF::SHF_ALLOC,
                          SectionKind::getDataRel());
   else
     EHFrameSection =
       Ctx->getCOFFSection(".eh_frame",
                           COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
                           COFF::IMAGE_SCN_MEM_READ |
                           COFF::IMAGE_SCN_MEM_WRITE,
                           SectionKind::getDataRel());
 }