lib.addMetaAttrs: use overrideAttrs when available

Previously, any subsequent change to a derivation after
an `addMetaAttrs` call would cause said attribute(s) to
be unconditionally reset back to their previous value(s):

    nix-repl> ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
    error:
        … while evaluating the attribute 'meta.priority'
            at /nix/store/nxdiklm6dnf9pma1zg7srls2nzrykrjf-nixos/nixos/pkgs/stdenv/generic/make-derivation.nix:846:17:
            845|         inherit passthru overrideAttrs;
            846|         inherit meta;
                |                 ^
            847|       }

        error: attribute 'priority' missing
        at «string»:1:67:
                1| ((oldPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
                |                                                                   ^

This change makes it so that this does not happen (unless, of
course, a subsequent override does affect those values):

    nix-repl> ((newPkgs.lib.lowPrio oldPkgs.hello).overrideAttrs {a = 1;}).meta.priority
    10

Fixes #323624.

0 files changed, 0 insertions, 0 deletions