Add nix build

Modifies the flake and Makefile to be proper, letting nix build work.

Makefile

@@ -1,15 +1,22 @@
+# until gcc has "#embed" support
 CC=clang
 CFLAGS=-std=c23 -O3 -Wpedantic -Wall -Wextra -g
 
 .PHONY: all
-all: kvm_sectorlisp sectorlisp/sectorlisp.bin
+all: kvm_sectorlisp
 
 .PHONY: clean
 clean:
-	$(RM) kvm_sectorlisp sectorlisp/sectorlisp.bin
+	$(RM) kvm_sectorlisp sectorlisp.bin
+	$(MAKE) -C sectorlisp clean
 
-sectorlisp/sectorlisp.bin:
+kvm_sectorlisp: kvm_sectorlisp.c sectorlisp.bin
+	$(CC) kvm_sectorlisp.c -o kvm_sectorlisp $(CFLAGS)
+
+sectorlisp.bin: sectorlisp
+	ln -sf sectorlisp/sectorlisp.bin sectorlisp.bin
+
+.PHONY: sectorlisp
+sectorlisp:
 	$(MAKE) -C sectorlisp sectorlisp.bin
 
-kvm_sectorlisp: kvm_sectorlisp.c
-	$(CC) kvm_sectorlisp.c -o kvm_sectorlisp $(CFLAGS)

flake.nix

@@ -8,20 +8,27 @@
   outputs = { self, nixpkgs }:
     let
       pkgs = nixpkgs.legacyPackages.x86_64-linux;
+      stdenv = pkgs.llvmPackages_19.stdenv;
     in
     {
-      devShells.x86_64-linux.default = pkgs.mkShell {
-          name = "KVM Sectorlisp Shell";
-          nativeBuildInputs = with pkgs; with llvmPackages_19; [
-            clang-tools
-            clang
-          ];
-          packages = with pkgs; with llvmPackages_19; [
-            gdb
-            binutils
-            blink
-            git
-          ];
-        };
+      devShells.x86_64-linux.default = pkgs.mkShell.override {inherit stdenv;} {
+        name = "KVM Sectorlisp Shell";
+        packages = with pkgs; with llvmPackages_19; [
+          gdb
+          blink
+          binutils
+          git
+          clang-tools
+        ];
+      };
+      defaultPackage.x86_64-linux = stdenv.mkDerivation {
+        name = "KVM Sectorlisp";
+        version = "1.0.0";
+        src = ./.;
+        installPhase = ''
+          mkdir -p $out/bin
+          mv kvm_sectorlisp $out/bin
+        '';
+      };
     };
 }

kvm_sectorlisp.c

@@ -15,7 +15,7 @@
 #define GET_IO_ADDR(kvm_run) (((uint8_t *)kvm_run) + kvm_run->io.data_offset)
 
 static const uint8_t SECTORLISP_BIN[] = {
-#embed "sectorlisp/sectorlisp.bin"
+#embed "sectorlisp.bin"
 };
 
 // uncomfortable global vars

readme.md

@@ -9,3 +9,14 @@ Requirements:
 - To compile: clang 19+ (to support C23's `#embed` feature)
 
 Great thanks to the [LWN post on the KVM API](https://lwn.net/Articles/658511/) for acting as a guide.
+
+## Building
+```
+git clone --recurse-submodules
+make
+```
+Clang 19 is the only dependency (for C23 support).
+
+### NixOS Notes
+
+To build for NixOS, run `nix build '.?submodules=1'`. See [discourse for why](https://discourse.nixos.org/t/get-nix-flake-to-include-git-submodule/30324/16).