feat: port gcc to MontaukOS

GNUmakefile

@@ -156,6 +156,13 @@ run-hdd-bios: $(IMAGE_NAME).hdd
 toolchain:
 	./toolchain/build-toolchain.sh
 
+# Build the Montauk SDK: native binutils + GCC that run on MontaukOS,
+# shipped into the image at 0:/sdk by the programs/ devkit target.
+# One-time (long) build; idempotent afterwards.
+.PHONY: sdk
+sdk:
+	./toolchain/build-native-sdk.sh
+
 limine/limine:
 	rm -rf limine
 	git clone https://github.com/limine-bootloader/limine.git --branch=v9.x-binary --depth=1