Allow to use -fsanitize=address for iOS simulator

[glider]

Summary

This patch lets the users invoke clang -fsanitize=address to link binaries targeting the iOS simulator.

[kcc]

LGTM

[Eugene.Zelenko]

Committed in rL177633.

lib/Driver/ToolChains.cpp

if (isTargetIPhoneOS()) {
       // The Ubsan runtime library requires C++.
       AddCXXStdlibLibArgs(Args, CmdArgs);
     }
   }
 
   // Add ASAN runtime library, if required. Dynamic libraries and bundles
   // should not be linked with the runtime library.
   if (Sanitize.needsAsanRt()) {
+    if (isTargetIPhoneOS() && !isTargetIOSSimulator()) {
+      getDriver().Diag(diag::err_drv_clang_unsupported_per_platform)
+        << "-fsanitize=address";
+    } else {
       if (Args.hasArg(options::OPT_dynamiclib) ||
           Args.hasArg(options::OPT_bundle)) {
         // Assume the binary will provide the ASan runtime.
-    } else if (isTargetIPhoneOS()) {
-      getDriver().Diag(diag::err_drv_clang_unsupported_per_platform)
-        << "-fsanitize=address";
       } else {
-      AddLinkRuntimeLib(Args, CmdArgs, "libclang_rt.asan_osx_dynamic.dylib", true);
-
+        AddLinkRuntimeLib(Args, CmdArgs,
+                          "libclang_rt.asan_osx_dynamic.dylib", true);
         // The ASAN runtime library requires C++.
         AddCXXStdlibLibArgs(Args, CmdArgs);
       }
     }
+  }
 
   // Otherwise link libSystem, then the dynamic runtime library, and finally any
   // target specific static runtime library.
   CmdArgs.push_back("-lSystem");
 
   // Select the dynamic runtime library and the target specific static library.
   if (isTargetIPhoneOS()) {
     // If we are compiling as iOS / simulator, don't attempt to link libgcc_s.1,