Apply suggestion from @zanieb

Author: zanieb

Modules/_posixsubprocess.c

@@ -436,6 +436,9 @@ _close_open_fds_safe(int start_fd, int *fds_to_keep, Py_ssize_t fds_to_keep_len)
         Py_ssize_t bytes;
         while (1) {
 #ifdef HAVE_GETDENTS64
+            # musl <1.2.4 headers expose `getdents64` as an alias for `getdents`, whose buffer parameter
+            # is `struct dirent *`. We use `void *` to support both that interface and the glibc declaration
+            # without an incompatible-pointer diagnostic.
             bytes = getdents64(fd_dir_fd, (void *)buffer, sizeof(buffer));
 #else
             bytes = syscall(SYS_getdents64, fd_dir_fd,