ELF: skip visited segments in compute_symbols_from_segment()

[pelijah]

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Detailed description

I am not familiar with ELF format but I think it is enough to memorize offset of visited symbol segments.
Related: #4386

[ret2libc]

I'm honestly not sure if there are downsides to this. Could we have overlapping segments? That's the only edge case I can think of.

[XVilka]

LGTM, it doesn't break anything I tried so far. Could always revert if counterexamples are found.

[XVilka]

@wargio could you please take a look and lets merge it if you have no objections.