Use file descriptor I/O for process pipes

Use low level non-blocking I/O for process pipe streams. This may fix issues with data not getting through the pipe occasionally.

Related: https://github.com/libsdl-org/SDL/issues/11006

src/process/posix/SDL_posixprocess.c

@@ -57,12 +57,7 @@ static bool SetupStream(SDL_Process *process, int fd, const char *mode, const ch
     // Set the file descriptor to non-blocking mode
     fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
 
-    FILE *fp = fdopen(fd, mode);
-    if (!fp) {
-        return false;
-    }
-
-    SDL_IOStream *io = SDL_IOFromFP(fp, true);
+    SDL_IOStream *io = SDL_IOFromFD(fd, true);
     if (!io) {
         return false;
     }