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/Wine.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace VRCX;
+
+public static class Wine
+{
+    [DllImport("ntdll.dll")]
+    private static extern IntPtr wine_get_version();
+
+    public static bool GetIfWine()
+    {
+        // wine_get_version should be guaranteed to exist exclusively in Wine envs,
+        // unlike some other suggestions like checking Wine registry keys 
+        try
+        {
+            wine_get_version();
+            return true;
+        }
+        catch { return false; }
+    }
+}
+