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GH-40394: [C++] Add support for mold (#40397)

### Rationale for this change

mold is a faster linker. It will reduce build time.

mold supports only ELF. So it's available on only Linux and *BSD. 

### What changes are included in this PR?

Add new `ARROW_USE_MOLD` CMake option. It's `OFF` by default because it doesn't work with conda.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #40394

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>