kill: Parse CLI arguments using Arguments.strings

The previous implementation used argv and LibC to parse arguments,
it now uses the Arguments.strings interface to do so.

Userland/Utilities/kill.cpp

@@ -12,7 +12,6 @@
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <unistd.h>
 
 static void print_usage_and_exit()
@@ -27,9 +26,9 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     TRY(Core::System::pledge("stdio proc"));
 
     int argc = arguments.argc;
-    char** argv = arguments.argv;
+    auto strings = arguments.strings;
 
-    if (argc == 2 && !strcmp(argv[1], "-l")) {
+    if (argc == 2 && strings[1] == "-l") {
         for (size_t i = 0; i < NSIG; ++i) {
             if (i && !(i % 5))
                 outln("");
@@ -45,29 +44,29 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     int pid_argi = 1;
     if (argc == 3) {
         pid_argi = 2;
-        if (argv[1][0] != '-')
+        if (strings[1][0] != '-')
             print_usage_and_exit();
 
         Optional<unsigned> number;
 
-        if (isalpha(argv[1][1])) {
-            int value = getsignalbyname(&argv[1][1]);
+        if (isalpha(strings[1][1])) {
+            int value = getsignalbyname(&strings[1][1]);
             if (value >= 0 && value < NSIG)
                 number = value;
         }
 
         if (!number.has_value())
-            number = StringView(&argv[1][1]).to_uint();
+            number = strings[1].substring_view(1, 1).to_uint();
 
         if (!number.has_value()) {
-            warnln("'{}' is not a valid signal name or number", &argv[1][1]);
+            warnln("'{}' is not a valid signal name or number", &strings[1][1]);
             return 2;
         }
         signum = number.value();
     }
-    auto pid_opt = String(argv[pid_argi]).to_int();
+    auto pid_opt = strings[pid_argi].to_int();
     if (!pid_opt.has_value()) {
-        warnln("'{}' is not a valid PID", argv[pid_argi]);
+        warnln("'{}' is not a valid PID", strings[pid_argi]);
         return 3;
     }
     pid_t pid = pid_opt.value();