docs: Fixed some Emscripten details

docs/README-emscripten.md

@@ -223,12 +223,12 @@ If you aren't developing SDL itself, have a desire to mess with its source
 code, or need something on the bleeding edge, don't build SDL. Just use
 Emscripten's packaged version!
 
-Compile and link your app with `-s USE_SDL=2` and it'll use a build of
+Compile and link your app with `-sUSE_SDL=2` and it'll use a build of
 SDL packaged with Emscripten. This comes from the same source code and
 fixes the Emscripten project makes to SDL are generally merged into SDL's
 revision control, so often this is much easier for app developers.
 
-`-s USE_SDL=1` will select Emscripten's JavaScript reimplementation of SDL
+`-sUSE_SDL=1` will select Emscripten's JavaScript reimplementation of SDL
 1.2 instead; if you need SDL 1.2, this might be fine, but we generally
 recommend you don't use SDL 1.2 in modern times.
 
@@ -253,14 +253,14 @@ tools.
 cd SDL
 mkdir build
 cd build
-emconfigure ../configure --host=wasm32-unknown-emscripten --disable-pthreads --disable-assembly --disable-cpuinfo CFLAGS="-s USE_SDL=0 -O3"
+emconfigure ../configure --host=wasm32-unknown-emscripten --disable-pthreads --disable-assembly --disable-cpuinfo CFLAGS="-sUSE_SDL=0 -O3"
 emmake make -j4
 ```
 
 If you want to build with thread support, something like this works:
 
 ```bash
-emconfigure ../configure --host=wasm32-unknown-emscripten --enable-pthreads --disable-assembly --disable-cpuinfo CFLAGS="-s USE_SDL=0 -O3 -pthread" LDFLAGS="-pthread"
+emconfigure ../configure --host=wasm32-unknown-emscripten --enable-pthreads --disable-assembly --disable-cpuinfo CFLAGS="-sUSE_SDL=0 -O3 -pthread" LDFLAGS="-pthread"
 ```
 
 Or with cmake:
@@ -285,7 +285,7 @@ You need to compile with `emcc` instead of `gcc` or `clang` or whatever, but
 mostly it uses the same command line arguments as Clang.
 
 Link against the SDL/build/.libs/libSDL2.a file you generated by building SDL,
-link with `-s USE_SDL=2` to use Emscripten's prepackaged SDL2 build.
+link with `-sUSE_SDL=2` to use Emscripten's prepackaged SDL2 build.
 
 Usually you would produce a binary like this:
 
@@ -296,7 +296,7 @@ gcc -o mygame mygame.c  # or whatever
 But for Emscripten, you want to output something else:
 
 ```bash
-gcc -o index.html mygame.c  # or whatever
+emcc -o index.html mygame.c
 ```
 
 This will produce several files...support Javascript and WebAssembly (.wasm)
@@ -305,8 +305,8 @@ runs your app. You will (probably) eventually want to replace or customize
 that file and do `-o index.js` instead to just build the code pieces.
 
 If you're working on a program of any serious size, you'll likely need to
-link with `-s ALLOW_MEMORY_GROWTH=1 -s MAXIMUM_MEMORY=1gb` to get access
-to more memory. If using pthreads, you'll need the `-s MAXIMUM_MEMORY=1gb`
+link with `-sALLOW_MEMORY_GROWTH=1 -sMAXIMUM_MEMORY=1gb` to get access
+to more memory. If using pthreads, you'll need the `-sMAXIMUM_MEMORY=1gb`
 or the app will fail to start on iOS browsers, but this might be a bug that
 goes away in the future.