Originally reported as https://github.com/doublep/eldev/issues/76
but apparently boils down to the fact that Emacs 29 no longer byte-
compiles `.el' files in installed packages. I managed to reproduce the
original problem with `silex/emacs:master' Docker image.

To reproduce with Emacs only:

cat >does-install-byte-compile.el <<EOF
(setf package-user-dir (make-temp-file "emacs-packages" t))
(require 'package)
(package-initialize t)
(package-install 'dash)
(message "%S" (byte-code-function-p (symbol-function '-each)))
EOF

emacs --batch --load does-install-byte-compile.el

If the file is byte-compiled, the last line should read as "t". With all
images I have tested, this is the case. But Emacs 29 (i.e. that `:master'
image), it reads "nil" instead.

Paul