Userland: Fix 64-bit portability issues

Author: https://github.com/gunnarbeutner
Commit: b613817bca
Pull-request: https://github.com/SerenityOS/serenity/pull/6803
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/awesomekling

Userland/Utilities/w.cpp

@@ -10,6 +10,7 @@
 #include <LibCore/DateTime.h>
 #include <LibCore/File.h>
 #include <LibCore/ProcessStatisticsReader.h>
+#include <inttypes.h>
 #include <pwd.h>
 #include <stdio.h>
 #include <sys/stat.h>
@@ -87,7 +88,7 @@ int main()
         if (stat(tty.characters(), &st) == 0) {
             auto idle_time = now - st.st_mtime;
             if (idle_time >= 0) {
-                builder.appendf("%llds", idle_time);
+                builder.appendf("%" PRIi64 "s", idle_time);
                 idle_string = builder.to_string();
             }
         }