Kernel/riscv64: Make the kernel compile

This commits inserts TODOs into all necessary places to make the kernel
compile on riscv64!

Kernel/Arch/riscv64/Panic.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2022, Timon Kruiper <timonkruiper@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/Processor.h>
+#include <Kernel/KSyms.h>
+#include <Kernel/Library/Panic.h>
+
+// FIXME: Merge the code in this file with Kernel/Library/Panic.cpp once the proper abstractions are in place.
+
+// Note: This is required here, since __assertion_failed should be out of the Kernel namespace,
+//       but the PANIC macro uses functions that require the Kernel namespace.
+using namespace Kernel;
+
+[[noreturn]] void __assertion_failed(char const* msg, char const* file, unsigned line, char const* func)
+{
+    critical_dmesgln("ASSERTION FAILED: {}", msg);
+    critical_dmesgln("{}:{} in {}", file, line, func);
+
+    // Used for printing a nice backtrace!
+    PANIC("Aborted");
+}