I alternatively run 24.5 and 25.0.50. Unfortunately, packages installed and compiled from 25.0.50 don't work with Emacs 24.5 (
cl-struct-define is a common culprit).
One trivial solution is to not byte-compile anything. That makes things pretty slow, though.
How can I use compiled packages (for performance) while using the same
.emacs.d for both 24.5 and 25.0.50? I'd also be ok with 24.5 ignoring the compiled files.