lib/libc: fix bug in parsing in getopt

getopt had an issue when parsing optional arguments if
they had a space between the opion and its value.

Request: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=291374

Author: Simon Wollwage

lib/libc/stdlib/getopt.c

@@ -107,12 +107,17 @@ getopt(int nargc, char * const nargv[], const char *ostr)
 		   entire next argument. */
 		if (*place)
 			optarg = place;
-		else if (oli[2] == ':')
+        else if (oli[2] == ':') {
 			/*
 			 * GNU Extension, for optional arguments if the rest of
 			 * the argument is empty, we return NULL
 			 */
-			optarg = NULL;
+		    if (nargc > (optind + 1)) {
+				optarg = nargv[++optind];
+			} else {
+				optarg = NULL;
+			}
+        }
 		else if (nargc > ++optind)
 			optarg = nargv[optind];
 		else {