[PATCH] cygport: allow for different package compression types and implement ZStandard decompression

[Achim Gratz]

Now that setup and calm know about Zstandard compression it's about time
we teach cygport the same.

https://repo.or.cz/cygport/rpm-style.git/commitdiff/303045744ba6159c6063786cf5b173d760f6298d

This patch keeps the current defaults in place, but allows one to set up
two environment variables to control how tar gets invoked during
packaging.  You could do that from either the cygport file or the
.cygport.conf file:

CYGPORT_TAR_CMD="env ZSTD_CLEVEL=19 tar -I zstd --group nobody:65534 --owner nobody:65534"
CYGPORT_TAR_EXT=".tar.zst"

While our packaged tar does not yet know about zst files the compressor
has top be named explicitly, eventually Eric will get around and release
a new version hopefully and then this can get automatic.  As
demonstrated above the facility can be used to do other useful things
besides changing the compression type and extension.


Regards,
Achim.
-- 
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