Bootloader: Start work on bootloader

I wrote a fast first stage bootloader and a installer to put it into
a disk image.

bootloader/installer/main.cpp

@@ -0,0 +1,41 @@
+#include "ELF.h"
+#include "GPT.h"
+
+#include <iostream>
+
+int main(int argc, char** argv)
+{
+	using namespace std::string_view_literals;
+
+	if (argc != 3)
+	{
+		std::fprintf(stderr, "usage: %s BOOTLOADER DISK_IMAGE}\n", argv[0]);
+		return 1;
+	}
+
+	ELFFile bootloader(argv[1]);
+	if (!bootloader.success())
+		return 1;
+
+	auto stage1 = bootloader.find_section(".stage1"sv);
+	auto stage2 = bootloader.find_section(".stage2"sv);
+	if (!stage1.has_value() || !stage2.has_value())
+	{
+		std::cerr << bootloader.path() << " doesn't contain .stage1 and .stage2 sections" << std::endl;
+		return 1;
+	}
+
+	GPTFile disk_image(argv[2]);
+	if (!disk_image.success())
+		return 1;
+
+	if (!disk_image.install_bootcode(*stage1))
+		return 1;
+	std::cout << "wrote stage1 bootloader" << std::endl;
+
+	if (!disk_image.write_partition(*stage2, bios_boot_guid))
+		return 1;
+	std::cout << "wrote stage2 bootloader" << std::endl;
+
+	return 0;
+}