title: Adding a Custom macosx.internal SDK
body: <p>Prime Objective: I want a setup where I can compile both with the standard SDK, and with a modified SDK for kernel development by passing the correct SDK into xcodebuild.</p>
  
  <p>When building a MacOS X kernel, the default SDK must be modified. These modifications then can interfere with normal app development.</p>
  
  <p>Apple obviously has a <code>macosx.internal</code> SDK for that purpose (and probably various other purposes). Can I hijack the SDKROOT=macosx.internal setting somehow?</p>
  
  <p>Simply putting a <code>macosx.internal</code> or <code>macosx.internal.sdk</code> folder into <code>$(xcode-select -p)Platforms/MacOSX.platform/Developer/SDKs</code> does not seem to do the trick.</p>
  
  <p>Am I missing something?</p>