Kernel: Pass trampolines instead of lambdas to create_kernel_process

With -Og, all calls to create_kernel_process were triggering -Wnonnull
when creating these lambdas that get implicitly converted to function
pointers. A different design of create_kernel_process to use
AK::Function instead might avoid this awkward behavior.

Kernel/Process.h

@@ -151,17 +151,19 @@ public:
         return current_thread ? &current_thread->process() : nullptr;
     }
 
+    template<typename EntryFunction>
+    static void kernel_process_trampoline(void* data)
+    {
+        EntryFunction* func = reinterpret_cast<EntryFunction*>(data);
+        (*func)();
+        delete func;
+    }
+
     template<typename EntryFunction>
     static RefPtr<Process> create_kernel_process(RefPtr<Thread>& first_thread, String&& name, EntryFunction entry, u32 affinity = THREAD_AFFINITY_DEFAULT)
     {
         auto* entry_func = new EntryFunction(move(entry));
-        return create_kernel_process(
-            first_thread, move(name), [](void* data) {
-                EntryFunction* func = reinterpret_cast<EntryFunction*>(data);
-                (*func)();
-                delete func;
-            },
-            entry_func, affinity);
+        return create_kernel_process(first_thread, move(name), &Process::kernel_process_trampoline<EntryFunction>, entry_func, affinity);
     }
 
     static RefPtr<Process> create_kernel_process(RefPtr<Thread>& first_thread, String&& name, void (*entry)(void*), void* entry_data = nullptr, u32 affinity = THREAD_AFFINITY_DEFAULT);
@@ -805,7 +807,6 @@ inline ProcessID Thread::pid() const
             VERIFY_NOT_REACHED();                                    \
         }                                                            \
     } while (0)
-
 }
 
 inline static String copy_string_from_user(const Kernel::Syscall::StringArgument& string)

Kernel/Tasks/FinalizerTask.cpp

@@ -9,20 +9,22 @@
 
 namespace Kernel {
 
+static void finalizer_task(void*)
+{
+    Thread::current()->set_priority(THREAD_PRIORITY_LOW);
+    for (;;) {
+        g_finalizer_wait_queue->wait_forever("FinalizerTask");
+
+        if (g_finalizer_has_work.exchange(false, AK::MemoryOrder::memory_order_acq_rel) == true)
+            Thread::finalize_dying_threads();
+    }
+};
+
 void FinalizerTask::spawn()
 {
     RefPtr<Thread> finalizer_thread;
-    Process::create_kernel_process(
-        finalizer_thread, "FinalizerTask", [](void*) {
-            Thread::current()->set_priority(THREAD_PRIORITY_LOW);
-            for (;;) {
-                g_finalizer_wait_queue->wait_forever("FinalizerTask");
-
-                if (g_finalizer_has_work.exchange(false, AK::MemoryOrder::memory_order_acq_rel) == true)
-                    Thread::finalize_dying_threads();
-            }
-        },
-        nullptr);
+    auto finalizer_process = Process::create_kernel_process(finalizer_thread, "FinalizerTask", finalizer_task, nullptr);
+    VERIFY(finalizer_process);
     g_finalizer = finalizer_thread;
 }