Kernel: Add FIOCLEX and FIONCLEX ioctls

These allow you to turn the close-on-exec flag on/off via ioctl().

Kernel/Syscalls/ioctl.cpp

@@ -19,6 +19,18 @@ ErrorOr<FlatPtr> Process::sys$ioctl(int fd, unsigned request, FlatPtr arg)
         description->set_blocking(TRY(copy_typed_from_user(Userspace<int const*>(arg))) == 0);
         return 0;
     }
+    if (request == FIOCLEX) {
+        m_fds.with_exclusive([&](auto& fds) {
+            fds[fd].set_flags(fds[fd].flags() | FD_CLOEXEC);
+        });
+        return 0;
+    }
+    if (request == FIONCLEX) {
+        m_fds.with_exclusive([&](auto& fds) {
+            fds[fd].set_flags(fds[fd].flags() & ~FD_CLOEXEC);
+        });
+        return 0;
+    }
     TRY(description->file().ioctl(*description, request, arg));
     return 0;
 }

Userland/Libraries/LibC/sys/ioctl_numbers.h

@@ -119,6 +119,8 @@ enum IOCtlNumber {
     FIBMAP,
     FIONBIO,
     FIONREAD,
+    FIOCLEX,
+    FIONCLEX,
     KCOV_SETBUFSIZE,
     KCOV_ENABLE,
     KCOV_DISABLE,