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

lib/Target/X86/X86Subtarget.h

Index: lib/Target/X86/X86Subtarget.h
===================================================================
--- lib/Target/X86/X86Subtarget.h	(revision 138335)
+++ lib/Target/X86/X86Subtarget.h	(working copy)
@@ -172,26 +172,20 @@
   const Triple &getTargetTriple() const { return TargetTriple; }
 
   bool isTargetDarwin() const { return TargetTriple.isOSDarwin(); }
-  bool isTargetFreeBSD() const {
-    return TargetTriple.getOS() == Triple::FreeBSD;
-  }
-  bool isTargetSolaris() const {
-    return TargetTriple.getOS() == Triple::Solaris;
-  }
+  bool isTargetFreeBSD() const { return TargetTriple.isOSFreeBSD(); }
+  bool isTargetSolaris() const { return TargetTriple.isOSSolaris(); }
 
   // ELF is a reasonably sane default and the only other X86 targets we
   // support are Darwin and Windows. Just use "not those".
   bool isTargetELF() const {
     return !isTargetDarwin() && !isTargetWindows() && !isTargetCygMing();
   }
-  bool isTargetLinux() const { return TargetTriple.getOS() == Triple::Linux; }
+  bool isTargetLinux() const { return TargetTriple.isOSLinux(); }
 
-  bool isTargetWindows() const { return TargetTriple.getOS() == Triple::Win32; }
-  bool isTargetMingw() const { return TargetTriple.getOS() == Triple::MinGW32; }
-  bool isTargetCygwin() const { return TargetTriple.getOS() == Triple::Cygwin; }
-  bool isTargetCygMing() const {
-    return isTargetMingw() || isTargetCygwin();
-  }
+  bool isTargetWindows() const { return TargetTriple.isOSWin32(); }
+  bool isTargetMingw() const { return TargetTriple.isOSMinGW32(); }
+  bool isTargetCygwin() const { return TargetTriple.isOSCygwin(); }
+  bool isTargetCygMing() const { return isTargetMingw() || isTargetCygwin(); }
 
   /// isTargetCOFF - Return true if this is any COFF/Windows target variant.
   bool isTargetCOFF() const {
@@ -204,7 +198,7 @@
   }
 
   bool isTargetEnvMacho() const {
-    return isTargetDarwin() || (TargetTriple.getEnvironment() == Triple::MachO);
+    return isTargetDarwin() || (TargetTriple.isEnvironmentMachO());
   }
 
   bool isTargetWin32() const {