Fix rpath on Linux to handle plugins libraries loading in Editor

#1941

Source/Tools/Flax.Build/Platforms/Linux/LinuxToolchain.cs

@@ -99,6 +99,18 @@ namespace Flax.Build.Platforms
                 //args.Add(string.Format("-Wl,-soname=\"{0}\"", soname));
             }
 
+            // Include any external folders into rpath for proper dlopen (eg. when opening Editor project with plugins)
+            if (options.LinkEnv.Output == LinkerOutput.SharedLibrary || options.LinkEnv.Output == LinkerOutput.Executable)
+            {
+                var originDir = Path.GetDirectoryName(outputFilePath);
+                foreach (var lib in options.LinkEnv.InputLibraries)
+                {
+                    var libDir = Path.GetDirectoryName(lib);
+                    if (libDir != originDir)
+                        args.Add($"-Wl,-rpath,\"{libDir}\"");
+                }
+            }
+
             args.Add(string.Format("-target {0}", ArchitectureName));
             args.Add(string.Format("--sysroot=\"{0}\"", ToolsetRoot.Replace('\\', '/')));