Fixed stdin/stdout/stderr declarations

examples/hello.c

@@ -2,6 +2,6 @@
 
 int main() {
   char hellostr[] = "Hello, World!\n";
-  sys_write(0, hellostr, sizeof(hellostr));
+  sys_write(stdout->fd, hellostr, sizeof(hellostr));
   return 0;
 }

src/liblinux.c

@@ -1,9 +1,23 @@
 #include <liblinux.h>
 #include <liblinux/syscall.h>
 
-FILE *stdin = {0}; // FIXME
+FILE __stdin_FILE = {
-FILE *stdout = {1};
+  .fd = 0
-FILE *stderr = {2};
+};
+
+FILE *stdin = &__stdin_FILE;
+
+FILE __stdout_FILE = {
+  .fd = 1
+};
+
+FILE *stdout = &__stdout_FILE;
+
+FILE __stderr_FILE = {
+  .fd = 2
+};
+
+FILE *stderr = &__stderr_FILE;
 
 _Noreturn void sys_exit(int status) {
   syscall(__NR_exit, status);