[PATCH] ar: Add --thin for creating thin archives

[Nick Clifton]

Hi Fangrui,

> On 2022-01-10, Fangrui Song wrote:
>> In many ar implementations (FreeBSD, elfutils, etc), ar -T has the
>> X/Open System Interface specified semantics. Therefore -T for thin
>> archives is not recommended for portability.
>>
>>    PR binutils/28759
>>    * ar.c (long_options): Add --thin.
>>    * binutils/testsuite/binutils-all/ar.exp: Add tests.
>>    * NEWS: Mention --thin.

Patch approved - please apply.

Cheers
   Nick