Discourage overriding the patch phase

[eljamm]

Overriding patchPhase is considered an anti-pattern because in doing so we'd be silently skipping patches.

In total, there are currently 224 ¹ overridden phases with at least one package (fbida) that has its patches shadowed ² :

`fbida` with `patchPhase` overridden

Running phase: patchPhase
patching script interpreter paths in scripts/fallback.pl
scripts/fallback.pl: interpreter directive changed from "#!/usr/bin/perl -w" to "/nix/store/cc9zsahxyx5my7bqid4dzkljw2dd9ygm-perl-5.42.0/bin/perl -w"
# ...

`fbida` with `postPatch`

Running phase: patchPhase
applying patch /nix/store/4xms3k103nid6ks4gzn5fsqmqgd8236q-function-parameters.patch
patching file jpeg/62/jpeglib.h
patching script interpreter paths in scripts/fallback.pl
scripts/fallback.pl: interpreter directive changed from "#!/usr/bin/perl -w" to "/nix/store/cc9zsahxyx5my7bqid4dzkljw2dd9ygm-perl-5.42.0/bin/perl -w"
# ...

Footnotes

1. rg -l -e "patchPhase = ''" -e 'patchPhase = "' pkgs | wc -l ↩

2. rg -l "patches = \[" $(rg -l -e "patchPhase = ''" -e 'patchPhase = "' pkgs) ↩