[ASan] Link with libclang_rt.asan_iossim_dynamic.dylib when targeting the iOS simulator.
Add a test.

llvm-svn: 194820
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index acd0bbd..7dc7342 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -329,8 +329,17 @@
         // The ASAN runtime library requires C++.
         AddCXXStdlibLibArgs(Args, CmdArgs);
       }
-      AddLinkRuntimeLib(Args, CmdArgs,
-                        "libclang_rt.asan_osx_dynamic.dylib", true);
+      if (isTargetMacOS()) {
+        AddLinkRuntimeLib(Args, CmdArgs,
+                          "libclang_rt.asan_osx_dynamic.dylib",
+                          true);
+      } else {
+        if (isTargetIOSSimulator()) {
+          AddLinkRuntimeLib(Args, CmdArgs,
+                            "libclang_rt.asan_iossim_dynamic.dylib",
+                            true);
+        }
+      }
     }
   }