[newlib-cygwin] Cygwin: kill(1): fix parsing of negative pid

[Takashi Yano]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=3815e9939b2f5f9c5448c13225ca86154d948744

commit 3815e9939b2f5f9c5448c13225ca86154d948744
Author: Christian Franke <christian.franke@t-online.de>
Date:   Sat Apr 12 15:51:53 2025 +0200

    Cygwin: kill(1): fix parsing of negative pid
    
    Signed-off-by: Christian Franke <christian.franke@t-online.de>

Diff:
---
 winsup/utils/kill.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/winsup/utils/kill.cc b/winsup/utils/kill.cc
index bcabcd47c..1e6ab5c4b 100644
--- a/winsup/utils/kill.cc
+++ b/winsup/utils/kill.cc
@@ -372,7 +372,9 @@ main (int argc, char **argv)
 	case '?':
 	  if (gotasig) /* this is a negative pid, go ahead */
 	    {
-	      --optind;
+	      /* Reset optind because it points to the next argument if and
+		 only if the pid has one digit. */
+	      optind = av - argv;
 	      goto out;
 	    }
 	  optreset = 1;