LibC: Correctly reset the getopt state on optind = 0

515f313 incorrectly made getopt only reset its state when `optind`
is set to 1. However, the Linux man page says that setting it to 0 also
reinitializes its state and additionally checks for some GNU extensions.
stress-ng relies on this behavior.

The POSIX man page only says that setting it to 0 results in undefined
behavior.

Author: spholz

Userland/Libraries/LibC/bits/getopt.h

@@ -17,7 +17,8 @@ extern int optopt;
 // Index of the next argument to process upon a getopt*() call.
 extern int optind;
 // If set, reset the internal state kept by getopt*(). You may also want to set
-// optind to 1 in that case.
+// optind to 1 in that case. Alternatively, setting optind to 0 is treated like
+// doing both of the above.
 extern int optreset;
 // After parsing an option that accept an argument, set to point to the argument
 // value.

Userland/Libraries/LibC/getopt.cpp

@@ -33,7 +33,7 @@ int getopt(int argc, char* const* argv, char const* short_options)
     for (auto i = 1; i < argc; ++i)
         s_args.append({ argv[i], strlen(argv[i]) });
 
-    if (optind == 1 || optreset == 1) {
+    if (optind <= 1 || optreset == 1) {
         s_parser.reset_state();
         optind = 1;
         optreset = 0;
@@ -75,7 +75,7 @@ int getopt_long(int argc, char* const* argv, char const* short_options, const st
         });
     }
 
-    if (optind == 1 || optreset == 1) {
+    if (optind <= 1 || optreset == 1) {
         s_parser.reset_state();
         optind = 1;
         optreset = 0;