The build script copies lldb-defines.h into the staging area but it gets
overwritten by version-header-fix.py. This flow assumes that the
lldb-defines.h from the source was writable originally (thus the copy
maintains that permission). This is problematic for systems that
integrate LLVM source as read only.
This change skips the initial copy of lldb-defines.h, which prevents
lldb build failures when the source is not writable.
a05b232076