Make framework-header-fix process copied headers
Previously the framework-header-fix script would change the sources
before they were copied, leading to unnecessary rebuilds on repeat
ninja lldb invocations. This runs the script on the headers after
they're copied into the produced LLDB.framework, meaning it doesn't
affect any files being built.
Patch by Keith Smiley <firstname.lastname@example.org>!
Differential Revision: https://reviews.llvm.org/D49779