[cmake] Pass CMAKE_MAKE_PROGRAM to native configure

If the make program isn't in the path, the native configure will fail.
Pass CMAKE_MAKE_PROGRAM to the native configure explicitly to remedy
this, similar to what's already done for external project configuration.
Explicitly set CMAKE_MAKE_PROGRAM before the user flags so that they can
override it for the native build if they desire (though I can't fathom
why that would be useful).

llvm-svn: 322032