[AppleObjCRuntime] Don't bother looking for the runtime on non-apple targets

[labath]

Summary

This short-circuits the GetObjCVersion function to avoid iterating through target modules on
non-apple targets. This function is called on every Process::IsDynamicValue call, so this
overhead is not negligible.

[clayborg]

This is really the fault of AppleObjCRuntimeV1::CreateInstance() and AppleObjCRuntimeV2::CreateInstance() not checking the triple to begin with, but this is a simple solution that will effectively fix both places. Looks good.

lldb/trunk/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.cpp

 //------------------------------------------------------------------
 // Static Functions
 //------------------------------------------------------------------
 ObjCLanguageRuntime::ObjCRuntimeVersions
 AppleObjCRuntime::GetObjCVersion (Process *process, ModuleSP &objc_module_sp)
 {
     if (!process)
         return ObjCRuntimeVersions::eObjC_VersionUnknown;
-        
     Target &target = process->GetTarget();
+    if (target.GetArchitecture().GetTriple().getVendor() != llvm::Triple::VendorType::Apple)
+        return ObjCRuntimeVersions::eObjC_VersionUnknown;
+
     const ModuleList &target_modules = target.GetImages();
     Mutex::Locker modules_locker(target_modules.GetMutex());
     
     size_t num_images = target_modules.GetSize();
     for (size_t i = 0; i < num_images; i++)
     {
         ModuleSP module_sp = target_modules.GetModuleAtIndexUnlocked(i);
         // One tricky bit here is that we might get called as part of the initial module loading, but