libc: fix waitpid not detecting process termination

Since 452aa40770 and the change to
properly return processes exit codes in the status argument, the
status will never be EXIT_ZOMBIE(16) except a process was terminated by
signal(16).

Return from waitpid if either an error occurred (__res < 0) or
we got the status of a child process (__res == cpid).

Additionally fix the weird alignment of the closing braces.

libc/src/unistd/waitpid.c

@@ -1,6 +1,6 @@
 /// @file waitpid.c
 /// @brief
-/// @copyright (c) 2014-2023 This file is distributed under the MIT License.
+/// @copyright (c) 2014-2024 This file is distributed under the MIT License.
 /// See LICENSE.md for details.
 
 #include "sys/unistd.h"
@@ -18,19 +18,17 @@ pid_t waitpid(pid_t pid, int *status, int options)
     int __status = 0;
     do {
         __inline_syscall3(__res, waitpid, pid, &__status, options);
-        if (__res < 0) {
+        if (__res != 0) {
             break;
-}
+        }
-        if (__status == EXIT_ZOMBIE) {
-            break;
-}
         if (options && WNOHANG) {
             break;
-}
+        }
     } while (1);
+
     if (status) {
         *status = __status;
-}
+    }
     __syscall_return(pid_t, __res);
 }