See UPDATING about upgrading clang for dynamic linking.
. allow executables on ramdisk to be dynamically linked; this means
putting a few required shared libraries and ld.elf_so on the ramdisk.
. this makes the ramdisk (usage) smaller when they are dynamic, but
bigger when they're not.
. also we can safely ditch newroot and call mount directly as that is
all newroot does.
. create proto.common to share a bunch of entries between
small/nonsmall cases
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