Linux: Use NSIS installer (#991)

* feat: Implement SKIP_SHORTCUT for installer

* feat: Update Linux install script to use NSIS-based installer instead

* feat: Wine detection for installer shortcut suppression

* fix: Revert WINEPREFIX back to XDG Home

Oops.

* fix(linux): Forgot to use the variable here

* fix(linux): Don't error if INSTALL_LOCATION exists but is empty

* fix(linux): "Program Files" has a space

Dotnet/Update.cs

@@ -35,6 +35,9 @@ namespace VRCX
 
         private static void Install()
         {
+            var setupArguments = "/S";
+            if (Wine.GetIfWine()) setupArguments += " /DISABLE_SHORTCUT=true";
+            
             try
             {
                 File.Move(Update_Executable, VRCX_Setup_Executable);
@@ -43,7 +46,7 @@ namespace VRCX
                     StartInfo = new ProcessStartInfo
                     {
                         FileName = VRCX_Setup_Executable,
-                        Arguments = "/S",
+                        Arguments = setupArguments,
                         UseShellExecute = true,
                         WorkingDirectory = Program.AppDataDirectory
                     }