Move SDL2_mixer optional dependencies to features (#5565)

ports/sdl2-mixer/CONTROL

@@ -1,4 +1,20 @@
 Source: sdl2-mixer
-Version: 2.0.2-5
+Version: 2.0.2-6
 Description: Multi-channel audio mixer library for SDL.
-Build-Depends: sdl2, libflac, mpg123, libmodplug, libvorbis
+Build-Depends: sdl2
+
+Feature: libflac
+Description: Support for FLAC audio format.
+Build-Depends: libflac
+
+Feature: mpg123
+Description: Support for MP3 audio format.
+Build-Depends: mpg123
+
+Feature: libmodplug
+Description: Support for MOD audio format.
+Build-Depends: libmodplug
+
+Feature: libvorbis
+Description: Support for OGG Vorbis audio format.
+Build-Depends: libvorbis

ports/sdl2-mixer/portfile.cmake

@@ -13,14 +13,34 @@ vcpkg_extract_source_archive_ex(
 )
 file(COPY ${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt DESTINATION ${SOURCE_PATH})
 
+set(USE_MP3 OFF)
+if("mpg123" IN_LIST FEATURES)
+    set(USE_MP3 ON)
+endif()
+
+set(USE_FLAC OFF)
+if("libflac" IN_LIST FEATURES)
+    set(USE_FLAC ON)
+endif()
+
+set(USE_MOD OFF)
+if("libmodplug" IN_LIST FEATURES)
+    set(USE_MOD ON)
+endif()
+
+set(USE_OGGVORBIS OFF)
+if("libvorbis" IN_LIST FEATURES)
+    set(USE_OGGVORBIS ON)
+endif()
+
 vcpkg_configure_cmake(
     SOURCE_PATH ${SOURCE_PATH}
     PREFER_NINJA
     OPTIONS
-        -DSDL_MIXER_ENABLE_MP3=ON       # mpg123
-        -DSDL_MIXER_ENABLE_FLAC=ON      # libflac
-        -DSDL_MIXER_ENABLE_MOD=ON       # libmodplug
-        -DSDL_MIXER_ENABLE_OGGVORBIS=ON # libvorbis 
+        -DSDL_MIXER_ENABLE_MP3=${USE_MP3}             # mpg123
+        -DSDL_MIXER_ENABLE_FLAC=${USE_FLAC}           # libflac
+        -DSDL_MIXER_ENABLE_MOD=${USE_MOD}             # libmodplug
+        -DSDL_MIXER_ENABLE_OGGVORBIS=${USE_OGGVORBIS} # libvorbis 
     OPTIONS_DEBUG
         -DSDL_MIXER_SKIP_HEADERS=ON
 )