libsForQt5.kdegraphics-thumbnailers: hardcode Ghostscript path

Fixes #153983.

pkgs/applications/kde/default.nix

@@ -120,7 +120,7 @@ let
       kdebugsettings = callPackage ./kdebugsettings.nix {};
       kdeconnect-kde = callPackage ./kdeconnect-kde.nix {};
       kdegraphics-mobipocket = callPackage ./kdegraphics-mobipocket.nix {};
-      kdegraphics-thumbnailers = callPackage ./kdegraphics-thumbnailers.nix {};
+      kdegraphics-thumbnailers = callPackage ./kdegraphics-thumbnailers {};
       kdenetwork-filesharing = callPackage ./kdenetwork-filesharing.nix {};
       kdenlive = callPackage ./kdenlive {};
       kdepim-addons = callPackage ./kdepim-addons.nix {};

pkgs/applications/kde/kdegraphics-thumbnailers/default.nix

@@ -1,5 +1,5 @@
 {
-  mkDerivation, lib, fetchpatch,
+  mkDerivation, lib, ghostscript, substituteAll,
   extra-cmake-modules, karchive, kio, libkexiv2, libkdcraw, kdegraphics-mobipocket
 }:
 
@@ -11,4 +11,13 @@ mkDerivation {
   };
   nativeBuildInputs = [ extra-cmake-modules ];
   buildInputs = [ karchive kio libkexiv2 libkdcraw kdegraphics-mobipocket ];
+
+  patches = [
+    # Hardcode patches to Ghostscript so PDF thumbnails work OOTB.
+    # Intentionally not doing the same for dvips because TeX is big.
+    (substituteAll {
+      gs = "${ghostscript}/bin/gs";
+      src = ./gs-paths.patch;
+    })
+  ];
 }

pkgs/applications/kde/kdegraphics-thumbnailers/gs-paths.patch

@@ -0,0 +1,22 @@
+diff --git a/ps/gscreator.cpp b/ps/gscreator.cpp
+index 5b84e49..cbb7c25 100644
+--- a/ps/gscreator.cpp
++++ b/ps/gscreator.cpp
+@@ -101,7 +101,7 @@ static const char *epsprolog =
+     "[ ] 0 setdash newpath false setoverprint false setstrokeadjust\n";
+ 
+ static const char * gsargs_ps[] = {
+-    "gs",
++    "@gs@",
+     "-sDEVICE=png16m",
+     "-sOutputFile=-",
+     "-dSAFER",
+@@ -120,7 +120,7 @@ static const char * gsargs_ps[] = {
+ };
+ 
+ static const char * gsargs_eps[] = {
+-    "gs",
++    "@gs@",
+     "-sDEVICE=png16m",
+     "-sOutputFile=-",
+     "-dSAFER",