gamescope: patch gamescopereaper path

pkgs/by-name/ga/gamescope/gamescopereaper.patch

@@ -0,0 +1,13 @@
+diff --git a/src/Utils/Process.cpp b/src/Utils/Process.cpp
+index 5688fb1..6cea8d8 100644
+--- a/src/Utils/Process.cpp
++++ b/src/Utils/Process.cpp
+@@ -392,7 +392,7 @@ namespace gamescope::Process
+     pid_t SpawnProcessInWatchdog( char **argv, bool bRespawn, std::function<void()> fnPreambleInChild )
+     {
+         std::vector<char *> args;
+-        args.push_back( (char *)"gamescopereaper" );
++        args.push_back( (char *)"@gamescopereaper@" );
+         if ( bRespawn )
+             args.push_back( (char *)"--respawn" );
+         args.push_back( (char *)"--" );

pkgs/by-name/ga/gamescope/package.nix

@@ -57,6 +57,8 @@ stdenv.mkDerivation (finalAttrs: {
   patches = [
     # Make it look for shaders in the right place
     ./shaders-path.patch
+    # patch relative gamescopereaper path with absolute
+    ./gamescopereaper.patch
   ];
 
   # We can't substitute the patch itself because substituteAll is itself a derivation,
@@ -65,6 +67,8 @@ stdenv.mkDerivation (finalAttrs: {
     substituteInPlace src/reshade_effect_manager.cpp --replace "@out@" "$out"
     # Patching shebangs in the main `libdisplay-info` build
     patchShebangs subprojects/libdisplay-info/tool/gen-search-table.py
+    # Replace gamescopereeaper with absolute path
+    substituteInPlace src/Utils/Process.cpp --subst-var-by "gamescopereaper" "$out/bin/gamescopereaper"
   '';
 
   mesonFlags = [