ELFError::MultipleTextSections is misleading, it can be thrown for zero sections

[ruuda]

There is the error ELFError::MultipleTextSections:

Multiple text sections, consider removing llc option: -function-sections

Which is returned in a single place, here:

rbpf/src/elf.rs

Lines 363 to 365 in b40643e

	if 1 != num_text_sections {
	return Err(ELFError::MultipleTextSections);
	}

The error message and name are misleading, because it can also be thrown when there is no text section at all. @enriquefynn and me just discovered this the hard way.

[Lichtso]

Yes, that should be fixed.