gimp: Use env attribute for environment variables

This is in preparation for __structuredAttrs.

pkgs/applications/graphics/gimp/default.nix

···
 
   doCheck = true;
 
-  env.NIX_CFLAGS_COMPILE = lib.optionalString stdenv.isDarwin "-DGDK_OSX_BIG_SUR=16";
+  env = {
+    NIX_CFLAGS_COMPILE = lib.optionalString stdenv.isDarwin "-DGDK_OSX_BIG_SUR=16";
 
-  # Check if librsvg was built with --disable-pixbuf-loader.
-  PKG_CONFIG_GDK_PIXBUF_2_0_GDK_PIXBUF_MODULEDIR = "${librsvg}/${gdk-pixbuf.moduleDir}";
+    # Check if librsvg was built with --disable-pixbuf-loader.
+    PKG_CONFIG_GDK_PIXBUF_2_0_GDK_PIXBUF_MODULEDIR = "${librsvg}/${gdk-pixbuf.moduleDir}";
+  };
 
   preConfigure = ''
     # The check runs before glib-networking is registered

pkgs/applications/graphics/gimp/plugins/default.nix

···
         install -Dt "$pluginDir" "$@"
       }
     '';
-
-    # Override installation paths.
-    PKG_CONFIG_GIMP_2_0_GIMPLIBDIR = "${placeholder "out"}/${gimp.targetLibDir}";
-    PKG_CONFIG_GIMP_2_0_GIMPDATADIR = "${placeholder "out"}/${gimp.targetDataDir}";
   }
   // attrs
   // {
-      name = "${gimp.pname}-plugin-${name}";
-      buildInputs = [
-        gimp
-        gimp.gtk
-        glib
-      ] ++ (attrs.buildInputs or []);
+    name = "${gimp.pname}-plugin-${name}";
+    buildInputs = [
+      gimp
+      gimp.gtk
+      glib
+    ] ++ (attrs.buildInputs or []);
+
+    nativeBuildInputs = [
+      pkg-config
+      intltool
+    ] ++ (attrs.nativeBuildInputs or []);
 
-      nativeBuildInputs = [
-        pkg-config
-        intltool
-      ] ++ (attrs.nativeBuildInputs or []);
-    }
-  );
+    # Override installation paths.
+    env = {
+      PKG_CONFIG_GIMP_2_0_GIMPLIBDIR = "${placeholder "out"}/${gimp.targetLibDir}";
+      PKG_CONFIG_GIMP_2_0_GIMPDATADIR = "${placeholder "out"}/${gimp.targetDataDir}";
+    } // attrs.env or { };
+  });
 
   scriptDerivation = {src, ...}@attrs : pluginDerivation ({
     prePhases = "extraLib";
···
       url = "https://ftp.gimp.org/pub/gimp/plug-ins/v2.6/gap/gimp-gap-2.6.0.tar.bz2";
       sha256 = "1jic7ixcmsn4kx2cn32nc5087rk6g8xsrz022xy11yfmgvhzb0ql";
     };
-    NIX_LDFLAGS = "-lm";
+
     hardeningDisable = [ "format" ];
+
+    env = {
+      NIX_LDFLAGS = "-lm";
+    };
+
     meta = with lib; {
       description = "The GIMP Animation Package";
       homepage = "https://www.gimp.org";
···
     pname = "wavelet-sharpen";
     version = "0.1.2";
 
-    # Workaround build failure on -fno-common toolchains like upstream
-    # gcc-10. Otherwise build fails as:
-    #   ld: interface.o:(.bss+0xe0): multiple definition of `fimg'; plugin.o:(.bss+0x40): first defined here
-    env.NIX_CFLAGS_COMPILE = "-fcommon";
-    NIX_LDFLAGS = "-lm";
     src = fetchurl {
       url = "https://github.com/pixlsus/registry.gimp.org_static/raw/master/registry.gimp.org/files/wavelet-sharpen-0.1.2.tar.gz";
       sha256 = "0vql1k67i21g5ivaa1jh56rg427m0icrkpryrhg75nscpirfxxqw";
     };
+
+    env = {
+      # Workaround build failure on -fno-common toolchains like upstream
+      # gcc-10. Otherwise build fails as:
+      #   ld: interface.o:(.bss+0xe0): multiple definition of `fimg'; plugin.o:(.bss+0x40): first defined here
+      NIX_CFLAGS_COMPILE = "-fcommon";
+      NIX_LDFLAGS = "-lm";
+    };
+
     installPhase = "installPlugin src/wavelet-sharpen"; # TODO translations are not copied .. How to do this on nix?
   };