Shell: Use pledge()

Shell/main.cpp

@@ -843,6 +843,11 @@ void save_history()
 
 int main(int argc, char** argv)
 {
+    if (pledge("stdio rpath wpath cpath proc exec tty", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
     g.uid = getuid();
     g.sid = setsid();
     tcsetpgrp(0, getpgrp());