Merge pull request #291909 from cdmistman/lib-meta-available-on-doc-example

lib.meta.availableOn: add example in documentation

Changed files
+4
lib
+4
lib/meta.nix
···
platform, or `meta.platforms` is not present.
2. None of `meta.badPlatforms` pattern matches the given platform.
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+
Example:
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lib.meta.availableOn { system = "aarch64-darwin"; } pkg.zsh
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=> true
*/
availableOn = platform: pkg:
((!pkg?meta.platforms) || any (platformMatch platform) pkg.meta.platforms) &&