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

lib/Target/TargetLibraryInfo.cpp

 //===-- TargetLibraryInfo.cpp - Runtime library information ----------------==//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TargetLibraryInfo class.
@@ skipping 13 matching lines @@
 /// specified target triple.  This should be carefully written so that a missing
 /// target triple gets a sane set of defaults.
 static void initialize(TargetLibraryInfo &TLI, const Triple &T) {
   initializeTargetLibraryInfoPass(*PassRegistry::getPassRegistry());
 
   
   // memset_pattern16 is only available on iOS 3.0 and Mac OS/X 10.5 and later.
   if (T.isMacOSX()) {
     if (T.isMacOSXVersionLT(10, 5))
       TLI.setUnavailable(LibFunc::memset_pattern16);
-  } else if (T.getOS() == Triple::IOS) {
+  } else if (T.isOSIOS()) {
     if (T.isOSVersionLT(3, 0))
       TLI.setUnavailable(LibFunc::memset_pattern16);
   } else {
     TLI.setUnavailable(LibFunc::memset_pattern16);
   }
 
   // iprintf and friends are only available on XCore and TCE.
   if (T.getArch() != Triple::xcore && T.getArch() != Triple::tce) {
     TLI.setUnavailable(LibFunc::iprintf);
     TLI.setUnavailable(LibFunc::siprintf);
@@ skipping 20 matching lines @@
   : ImmutablePass(ID) {
   memcpy(AvailableArray, TLI.AvailableArray, sizeof(AvailableArray));
 }
 
 
 /// disableAllFunctions - This disables all builtins, which is used for options
 /// like -fno-builtin.
 void TargetLibraryInfo::disableAllFunctions() {
   memset(AvailableArray, 0, sizeof(AvailableArray));
 }