libpng,libpng12: migrate to by-name (#480725)

pkgs/by-name/li/libpng/package.nix

@@ -5,6 +5,7 @@
   zlib,
   apngSupport ? true,
   testers,
+  darwin,
 }:
 
 assert zlib != null;
@@ -17,8 +18,11 @@ let
   };
   whenPatched = lib.optionalString apngSupport;
 
+  # libpng is a dependency of xcbuild. Avoid an infinite recursion by using a bootstrap stdenv
+  # that does not propagate xcrun.
+  stdenv' = if stdenv.hostPlatform.isDarwin then darwin.bootstrapStdenv else stdenv;
 in
-stdenv.mkDerivation (finalAttrs: {
+stdenv'.mkDerivation (finalAttrs: {
   pname = "libpng" + whenPatched "-apng";
   version = "1.6.53";
 

pkgs/by-name/li/libpng12/package.nix

@@ -14,7 +14,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   src = fetchurl {
     url = "mirror://sourceforge/libpng/libpng-${finalAttrs.version}.tar.xz";
-    sha256 = "1izw9ybm27llk8531w6h4jp4rk2rxy2s9vil16nwik5dp0amyqxl";
+    hash = "sha256-tGNfFbitzMitCTTupIXvWcxMriTQ8DAKmpQeUZdP/Mc=";
   };
 
   postPatch = lib.optionalString stdenv.hostPlatform.isDarwin ''

pkgs/top-level/all-packages.nix

@@ -7015,15 +7015,6 @@ with pkgs;
   libpeas = callPackage ../development/libraries/libpeas { };
   libpeas2 = callPackage ../development/libraries/libpeas/2.x.nix { };
 
-  libpng = callPackage ../development/libraries/libpng {
-    stdenv =
-      # libpng is a dependency of xcbuild. Avoid an infinite recursion by using a bootstrap stdenv
-      # that does not propagate xcrun.
-      if stdenv.hostPlatform.isDarwin then darwin.bootstrapStdenv else stdenv;
-  };
-
-  libpng12 = callPackage ../development/libraries/libpng/12.nix { };
-
   inherit
     (callPackages ../development/libraries/prometheus-client-c {
       stdenv = gccStdenv; # Required for darwin