[driver] Use the iOS target triple to infer the deployment target.
rdar://11409204

llvm-svn: 156489
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index cc1adb1..86fef4f 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -524,8 +524,14 @@
     // If no OSX or iOS target has been specified and we're compiling for armv7,
     // go ahead as assume we're targeting iOS.
     if (OSXTarget.empty() && iOSTarget.empty())
-      if (getDarwinArchName(Args) == "armv7")
-        iOSTarget = "0.0";
+      if (getDarwinArchName(Args) == "armv7") {
+        std::string iOSVersionMin;
+        unsigned Major, Minor, Micro;
+        getTriple().getiOSVersion(Major, Minor, Micro);
+        llvm::raw_string_ostream(iOSVersionMin)
+          << Major << '.' << Minor << '.' << Micro;
+        iOSTarget = iOSVersionMin;
+      }
 
     // Handle conflicting deployment targets
     //