LibJIT: Integrate GDB JIT Interface with ELF builders

Provide a function to create an ELF image in a format GDB expects.
Outside of ELF platforms this image doesn't make much sense, and in
MacOS a Mach-O memory image is required: see
https://chromium.googlesource.com/v8/v8.git/+/refs/heads/main/src/diagnostics/gdb-jit.cc#1802

Since GDB requires active runtime addresses for the code, copying the
generated code into the image will not help. Instead, `build_gdb_image`
writes the runtime addresses of the code into a NOBITS `.text` section.

Userland/Libraries/LibJIT/GDBUnsupported.cpp

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2023, Jesús Lapastora <cyber.gsuscode@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJIT/GDB.h>
+
+namespace JIT::GDB {
+Optional<FixedArray<u8>> build_gdb_image(ReadonlyBytes, StringView, StringView)
+{
+    return {};
+}
+}