tools/nolibc: getopt: Fix potential out of bounds access

Running clang-tidy on a program that uses getopt() from nolibc
this warning appears:

getopt.h:80:6: warning: Out of bound access to memory after the end of the string literal [clang-analyzer-security.ArrayBound]
80 |         if (optstring[i] == ':') {

This looks like a very unlikely case that an argument
inside of argv is being changed between getopt() calls.

Adding a check for d becoming 0 in the guard after the loop
stops getopt() getting far enough to access beyond the end
of the array and seems to correct the issue.

Fixes: bae3cd708e8a ("tools/nolibc: add getopt()")
Assisted-by: Claude:claude-4.6-sonnet # reproducer
Signed-off-by: Daniel Palmer <daniel@thingy.jp>
Link: https://patch.msgid.link/20260520111931.1027758-1-daniel@thingy.jp
[Thomas: clean up commit message a bit]
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

0 files changed, 0 insertions, 0 deletions