Commit fc72ae40e303 broke x86-64 build environment.

[Rob Landley]

You've made the ORC unwinder part of allnoconfig, which means trying to
build "make ARCH=x86_64 allnoconfig" requires installing a new package
(libelf-dev) or else the build breaks.

What's worse, if I go into menuconfig and switch it back to frame
pointer, the build STILL breaks:

$ make -j 8
Makefile:932: *** "Cannot generate ORC metadata for
CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or
elfutils-libelf-devel".  Stop.
$ grep UNWIND .config
# CONFIG_UNWINDER_ORC is not set
CONFIG_UNWINDER_FRAME_POINTER=y
# CONFIG_UNWINDER_GUESS is not set

As far as I can tell, x86-64 doesn't build anymore without libelf-dev.
It's a new hard requirement for the build.

Why?

Rob