[ELF] --why-live: Skip symbol at index 0 and section symbols, handle .eh_frame symbols (#177099)
Symbols of empty names can be matched by `--why-live='*'`, which are
generally not useful.
* The first entry in a symbol table (STB_LOCAL and undefined)
* `STT_SECTION` symbols (emitted by LLVM integrated assembler when
needed by relocations). These input section symbols will be demoted by
`demoteAndCopyLocalSymbols`, so technically not really live.
In addition, such symbols of non-allocable sections currently lead to
crashes: `whyLive` does not record the section, causing the second
iteration of the `while (true)` loop in printWhyLive to call
`std::get<Symbol *>(cur)` when `cur` is an `InputSectionBase *`.
In addition, handle GCC crtendS.o `__FRAME_END__`, which is defined
relative to a `.eh_frame` section created with
`__attribute__((used, section(".eh_frame")))`.
Fix #176890
(cherry picked from commit 1869b15a0569e4e0fa0b97ee462db4e826519d4f)
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