Maybe another solution would be to make the choice of builtin ramdisk
compression user-selectable, and default to no compression at all.
Indeed, in the default case, the builtin ramdisk is so small (950 bytes
uncompressed), that it probably wouldn't really matter anyways.
The only case where it matters is for developers of embedded systems who
want to replace the builtin ramdisk with a fully populated one, because
their boot loader does not support loading a "normal" initrd.
These people are (hopefully) knowledgeable enough to pick an appropriate
compressor (but there's still the issue of notifying them about the
change, obviously).
Btw, what *is* the standard work flow of supplying your own built-in
initramfs? Do such developers usually supply a directory tree, or do
they already cpio it before supplying it to the kernel? Or do they even
compress it themselves?