Don't include TargetConditionals.h when building for android.
Move the include of the Mac TargetConditionals.h file to after we've
checked if we're building for Android. Apparently this file doesn't
exist on all macs used to build android and the rest of android builds
fine without it, so including it there causes the build to fail. It
appears to only be used to test TARGET_OS_IPHONE which will never be
true on android.