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

lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

 //===-- X86AsmBackend.cpp - X86 Assembler Backend -------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCAsmBackend.h"
@@ skipping 425 matching lines @@
       return false;
     }
   }
 };
 
 } // end anonymous namespace
 
 MCAsmBackend *llvm::createX86_32AsmBackend(const Target &T, StringRef TT) {
   Triple TheTriple(TT);
 
-  if (TheTriple.isOSDarwin() || TheTriple.getEnvironment() == Triple::MachO)
+  if (TheTriple.isOSDarwin() || TheTriple.isEnvironmentMachO())
     return new DarwinX86_32AsmBackend(T);
 
   if (TheTriple.isOSWindows())
     return new WindowsX86AsmBackend(T, false);
 
   return new ELFX86_32AsmBackend(T, TheTriple.getOS());
 }
 
 MCAsmBackend *llvm::createX86_64AsmBackend(const Target &T, StringRef TT) {
   Triple TheTriple(TT);
 
-  if (TheTriple.isOSDarwin() || TheTriple.getEnvironment() == Triple::MachO)
+  if (TheTriple.isOSDarwin() || TheTriple.isEnvironmentMachO())
     return new DarwinX86_64AsmBackend(T);
 
   if (TheTriple.isOSWindows())
     return new WindowsX86AsmBackend(T, true);
 
   return new ELFX86_64AsmBackend(T, TheTriple.getOS());
 }