[lld] r257017 - ELF: Improve performance of string table construction.

[Rafael Espíndola via llvm-commits]

>>
>> r257017:
>> * strtab is 3916859 bytes
>> * link takes 0.317558552 seconds
>>
>> r257016:
>> * strtab is 3812950 bytes (1.027* smaller)
>> * link takes 0.353217270 seconds (1.11* slower)
>>
>> r257016 with StrTabBuilder.finalize commented out as a timing hack.
>> * link time is 0.331792363 (1.04X slower)
...

>
> What's the string table size when you disabled tail merging but did
> de-duplication?

It might be 3813075 bytes. I say might because I haven't finished the
patch and might have missed something.

The bug is pr26198.

Cheers,
Rafael