Merge commit 'dec0d4ec4153bf9fc2b78ae6c2df45b6ea8dde7a' as 'external/sdl/SDL'

external/sdl/SDL/INSTALL.txt

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+
+To compile and install SDL:
+
+    1.  Windows with Visual Studio:
+        * Read ./docs/README-visualc.md
+
+        Windows building with mingw-w64 for x86:
+        * Run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=build-scripts/cmake-toolchain-mingw64-i686.cmake && cmake --build build && cmake --install build
+
+        Windows building with mingw-w64 for x64:
+        * Run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=build-scripts/cmake-toolchain-mingw64-x86_64.cmake && cmake --build build && cmake --install build
+
+        macOS with Xcode:
+        * Read docs/README-macos.md
+
+        macOS from the command line:
+        * Run: cmake -S . -B build && cmake --build build && cmake --install build
+
+        Linux and other UNIX systems:
+        * Run: cmake -S . -B build && cmake --build build && cmake --install build
+
+        Android:
+        * Read docs/README-android.md
+
+        iOS:
+        * Read docs/README-ios.md
+
+        Using Cmake:
+        * Read docs/README-cmake.md
+
+    2.  Look at the example programs in ./test, and check out the online
+        documentation at https://wiki.libsdl.org/
+
+    3.  Join the SDL developer discussions, sign up on 
+        https://discourse.libsdl.org/
+        and go to the development forum
+        https://discourse.libsdl.org/c/sdl-development/6
+
+    4.  Sign up for the announcement list through the web interface:
+        https://www.libsdl.org/mailing-list.php
+
+That's it!
+Sam Lantinga <slouken@libsdl.org>