CI/MacOS: Install SDL2 and FFMPEG from externals

.ci/macos/build.sh

@@ -3,20 +3,25 @@
 set -o pipefail
 
 export Qt5_DIR=$(brew --prefix)/opt/qt5
-export PATH="/usr/local/opt/ccache/libexec:/usr/local/opt/llvm/bin:$PATH"
+export PATH="/usr/local/opt/ccache/libexec:$PATH"
 # ccache configurations
 export CCACHE_CPP2=yes
 export CCACHE_SLOPPINESS=time_macros
 
 export CC="ccache clang"
 export CXX="ccache clang++"
-export LDFLAGS="-L/usr/local/opt/llvm/lib"
-export CPPFLAGS="-I/usr/local/opt/llvm/include"
 
 ccache -s
 
 mkdir build && cd build
-cmake .. -DCMAKE_BUILD_TYPE=Release -DENABLE_QT_TRANSLATION=ON -DCITRA_ENABLE_COMPATIBILITY_REPORTING=${ENABLE_COMPATIBILITY_REPORTING:-"OFF"} -DENABLE_COMPATIBILITY_LIST_DOWNLOAD=ON -DUSE_DISCORD_PRESENCE=ON -DENABLE_FFMPEG_AUDIO_DECODER=ON -DENABLE_FFMPEG_VIDEO_DUMPER=ON -GNinja
+cmake .. -DCMAKE_BUILD_TYPE=Release \
+    -DENABLE_QT_TRANSLATION=ON \
+    -DCITRA_ENABLE_COMPATIBILITY_REPORTING=${ENABLE_COMPATIBILITY_REPORTING:-"OFF"} \
+    -DENABLE_COMPATIBILITY_LIST_DOWNLOAD=ON \
+    -DUSE_DISCORD_PRESENCE=ON \
+    -DENABLE_FFMPEG_AUDIO_DECODER=ON \
+    -DENABLE_FFMPEG_VIDEO_DUMPER=ON \
+    -GNinja
 ninja
 
 ccache -s

.ci/macos/deps.sh

@@ -3,5 +3,21 @@
 brew update
 brew unlink python@2 || true
 rm '/usr/local/bin/2to3' || true
-brew install qt5 sdl2 p7zip ccache ffmpeg llvm ninja || true
+brew install qt5 p7zip ccache ninja || true
 pip3 install macpack
+
+export SDL_VER=2.0.16
+export FFMPEG_VER=4.4
+
+mkdir tmp
+cd tmp/
+
+# install SDL
+wget https://github.com/SachinVin/ext-macos-bin/raw/main/sdl2/sdl-${SDL_VER}.7z
+7z x sdl-${SDL_VER}.7z
+cp -rv $(pwd)/sdl-${SDL_VER}/* /
+
+# install FFMPEG
+wget https://github.com/SachinVin/ext-macos-bin/raw/main/ffmpeg/ffmpeg-${FFMPEG_VER}.7z
+7z x ffmpeg-${FFMPEG_VER}.7z
+cp -rv $(pwd)/ffmpeg-${FFMPEG_VER}/* /