[PATCH cygport] lib/src_prep.cygpart: Fix incorrect options passed to unzstd in unpack()

[ASSI]

Yasutaka ATARASHI via Cygwin-apps writes:
> Yeah, I also wonder why the --keep option is not used for .gz and .bz2.
> Now, I recognized the reason.

Thanks.

> `unpack()` is expected to extract the files to the current working
> directory regardless of the specified path of the input. Please see
> the usage in `__src_prep()`.
> Therefore, --keep option can't be used simply.

That's true for bunzip2 and gunzip, but not for zstd (where the output
file can be independently specified).


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds