Revert part of r239007 related to creating the Python symlink.

This has apparently been broken since June, but only on non-Windows.
Perhaps nobody noticed it because if the symlink is already there
it won't try to re-create it, and nobody ever tried doing a clean
build.

In any case, I will let the original author attempt to fix this if
he is still interested.  the problem is that in the normal case
of not setting BUILD_SHARED_LIBS and simply running ninja, it would
link _lldb.so to a non-existent location, creating a dangling
symlink.

llvm-svn: 251840