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

lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp

 //===-- X86MCAsmInfo.cpp - X86 asm properties -----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the declarations of the X86MCAsmInfo properties.
@@ skipping 86 matching lines @@
   HasLEB128 = true;  // Target asm supports leb128 directives (little-endian)
 
   // Debug Information
   SupportsDebugInformation = true;
 
   // Exceptions handling
   ExceptionsType = ExceptionHandling::DwarfCFI;
 
   // OpenBSD has buggy support for .quad in 32-bit mode, just split into two
   // .words.
-  if (T.getOS() == Triple::OpenBSD && T.getArch() == Triple::x86)
+  if (T.isOSOpenBSD() && T.getArch() == Triple::x86)
     Data64bitsDirective = 0;
 }
 
 const MCExpr *
 X86_64MCAsmInfoDarwin::getExprForPersonalitySymbol(const MCSymbol *Sym,
                                                    unsigned Encoding,
                                                    MCStreamer &Streamer) const {
   MCContext &Context = Streamer.getContext();
   const MCExpr *Res =
     MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, Context);
@@ skipping 11 matching lines @@
   if (Triple.getArch() == Triple::x86_64) {
     GlobalPrefix = "";
     PrivateGlobalPrefix = ".L";
   }
 
   AsmTransCBE = x86_asm_table;
   AssemblerDialect = AsmWriterFlavor;
 
   TextAlignFillValue = 0x90;
 }