LibCore: Implement Core::System::lseek

Author: https://github.com/sin-ack
Commit: 301f4c469f
Pull-request: https://github.com/SerenityOS/serenity/pull/11991
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibCore/System.cpp

@@ -540,6 +540,14 @@ ErrorOr<pid_t> posix_spawnp(StringView const path, posix_spawn_file_actions_t* c
     return child_pid;
 }
 
+ErrorOr<off_t> lseek(int fd, off_t offset, int whence)
+{
+    off_t rc = ::lseek(fd, offset, whence);
+    if (rc < 0)
+        return Error::from_syscall("lseek", -errno);
+    return rc;
+}
+
 ErrorOr<WaitPidResult> waitpid(pid_t waitee, int options)
 {
     int wstatus;

Userland/Libraries/LibCore/System.h

@@ -87,6 +87,7 @@ ErrorOr<Optional<struct passwd>> getpwuid(uid_t);
 ErrorOr<Optional<struct group>> getgrgid(gid_t);
 ErrorOr<void> clock_settime(clockid_t clock_id, struct timespec* ts);
 ErrorOr<pid_t> posix_spawnp(StringView const path, posix_spawn_file_actions_t* const file_actions, posix_spawnattr_t* const attr, char* const arguments[], char* const envp[]);
+ErrorOr<off_t> lseek(int fd, off_t, int whence);
 
 struct WaitPidResult {
     pid_t pid;