curl: properly handle zstd support rather than just shutting it off

[Spudz76]

Fixes package libcurl build issue :

Package libcurl is missing dependencies for the following libraries:
libzstd.so.1

Previous patch by Hans Dedecker dedeckeh@gmail.com took the easy way out :)

Suggested-by: Syrone Wong wong.syrone@gmail.com
Signed-off-by: Tony Butler spudz76@gmail.com

[dedeckeh]

NACK, packages in the core repo (curl in this case) cannot depend on packages outside the core repo (zstd in packages repo in this case). Either zstd must be move to the core repo or curl must be moved to the packages repo; but since we want to move more packages to the feeds repo I don't think a consensus will be found to move zstd to the core the repo. So I did not take the easy way out taking the above into account as I wanted to deblock the situation.

[Spudz76]

Cool, yet another open source project forcing me to keep my own tree of patches.

So how about make a curl-full then, in packages repo, and apply every workable feature to it. Then I can uninstall base curl because I don't need to save space, and want zstd support, but don't want to maintain my own pile of patches.

Also remove all weird features core doesn't need curl to do so that it is painfully obvious if you want a curl that does everything you need to install packages feed and use curl-full instead. Similar to how vim works.

[BKPepe]

By default it is disabled, wouldn't it be sufficient to have it more documented for example: Enable zstd support (requires packages feed)?

[dedeckeh]

@BKPepe Documenting it more won't fix the issue that curl needs to depend on the external package zstd. But this discussion fits into the bigger picture of which packages do we want to move to packages feed and/or which packages from feeds/packages need to be moved to the core repo as core packages depend on it.

[neheb]

Why is curl in base? scripts/download.pl uses host not target curl.

[aparcar]

Related #3351

[dedeckeh]

Closing this PR as curl is moved to packages (openwrt/packages#13214)