Updated README-cmake.md with build instructions for several platforms

docs/README-cmake.md

@@ -20,37 +20,50 @@ The CMake build system is supported on the following platforms:
 * QNX 7.x/8.x
 * RiscOS
 
-## Building SDL
+# Building SDL on Windows
 
-Assuming the source tree of SDL is located at `~/sdl`,
-this will configure and build SDL in the `~/build` directory:
+Assuming you're in the SDL source directory, building and installing to C:/SDL can be done with:
 ```sh
-cmake -S ~/sdl -B ~/build
-cmake --build ~/build
+cmake .
+cmake --build . --config RelWithDebInfo
+cmake --install . --config RelWithDebInfo --prefix C:/SDL
 ```
 
-Installation can be done using:
+# Building SDL on UNIX
+
+SDL will build with very few dependencies, but for full functionality you should install the packages detailed in [README-linux.md](README-linux.md).
+
+Assuming you're in the SDL source directory, building and installing to /usr/local can be done with:
 ```sh
-cmake --install ~/build --prefix /usr/local        # '--install' requires CMake 3.15, or newer
+cmake .
+cmake --build .
+sudo cmake --install . --prefix /usr/local
 ```
 
-This will install SDL to /usr/local.
+# Building SDL on macOS
+
+Assuming you're in the SDL source directory, building and installing to ~/SDL can be done with:
+```sh
+cmake . -DSDL_FRAMEWORK=ON -DCMAKE_OSX_ARCHITECTURES="arm64;x86_64"
+cmake --build .
+cmake --install . --prefix ~/SDL
+```
 
 ### Building SDL tests
 
 You can build the SDL test programs by adding `-DSDL_TESTS=ON` to the first cmake command above:
 ```sh
-cmake -S ~/sdl -B ~/build -DSDL_TEST_LIBRARY=ON -DSDL_TESTS=ON
+cmake . -DSDL_TESTS=ON
 ```
-and then building normally. In this example, the test programs will be built and can be run from `~/build/tests/`.
+and then building normally. The test programs will be built and can be run from `test/`.
 
 ### Building SDL examples
 
 You can build the SDL example programs by adding `-DSDL_EXAMPLES=ON` to the first cmake command above:
 ```sh
-cmake -S ~/sdl -B ~/build -DSDL_EXAMPLES=ON
+cmake . -DSDL_EXAMPLES=ON
 ```
-and then building normally. In this example, the example programs will be built and can be run from `~/build/examples/`.
+and then building normally. The example programs will be built and can be run from `examples/`.
 
 ## Including SDL in your project