investigate system compatibility with built binaries

[ralexstokes]

we added binaries to the release CI flow but it looks like it may have some compatibility issues with some (older?) systems

bug report:

@ralexstokes I get this when running the compiled binary locally:
./mev: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.32' not found (required by ./mev)
./mev: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by ./mev)
./mev: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by ./mev)
Is it possible to build this with an earlier version of libc, so that it is compatible with distro's running older kernels

[ralexstokes]

from @michaelsproul

for Lighthouse we build with cross on an old Ubuntu version to get a binary that works across many distros

[michaelsproul]

More info:

https://github.com/sigp/lighthouse/blob/38514c07f222ff7783834c48cf5c0a6ee7f346d0/Makefile#L40-L54

Our Cross config:

https://github.com/sigp/lighthouse/blob/38514c07f222ff7783834c48cf5c0a6ee7f346d0/Cross.toml#L1-L2

Our docs:

https://lighthouse-book.sigmaprime.io/cross-compiling.html