using legacy SDL to avoid linking issues (otherwise link SDL2 as well, which is weird)

Author: Shchvova

README-macOS.md

@@ -16,7 +16,7 @@ CMake is used to configure the project. Download it [manually](https://cmake.org
 
 The easiest way of getting library dependencies is [MacPorts](https://www.macports.org/):
 ```sh
-port install libsdl  libsdl_gfx libsdl_image libsdl_mixer yaml-cpp
+port -N install libsdl -compat +legacy libsdl_gfx libsdl_image libsdl_mixer yaml-cpp
 ```
 
 Following instructions assume MacPorts is installed in default prefix `/opt/local`. If you installed ports into different location, replace it.

scripts/macports-config.yml

@@ -1,12 +1,14 @@
 version: '2.11.5'
-prefix: '/opt/local'
+prefix: /opt/local
 variants:
   select:
-    - aqua
-    - metal
-  deselect: x11
+    - universal
 ports:
   - name: libsdl
+    select:
+      - legacy
+    deselect:
+      - compat
   - name: libsdl_gfx
   - name: libsdl_image
   - name: libsdl_mixer