build: wrap nix build

These things currently require manual testing unfortunately since writing a nix stub would take a long time.

cmd/nixbuild/main.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"slices"
 	"strings"
 	"syscall"
 
@@ -20,6 +21,9 @@ type commandHandlerError string
 func (c commandHandlerError) Error() string { return string(c) }
 
 func main() {
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
 	var (
 		flagNixOS   bool
 		flagVerbose bool
@@ -38,7 +42,18 @@ func main() {
 		Flag(&flagVerbose, "v", command.BoolFlag(false), "Connect nix stderr").
 		Flag(&flagJSON, "json", command.BoolFlag(false), "Serialise output in JSON when applicable")
 
-	c.Command("instantiated", "Evaluate an installable and output all derivations it instantiated", func(args []string) error {
+	c.Command("build", "Build a list of installables", func(args []string) error {
+		if len(args) < 1 {
+			return commandHandlerError("build requires at least 1 argument")
+		}
+
+		if err := nixbuild.Build(ctx, slices.Values(args)); err != nil {
+			return commandHandlerError(fmt.Sprintf("cannot build: %v", err))
+		}
+		return nil
+	})
+
+	c.Command("instantiated", "Evaluate an installable and output all derivations instantiated during evaluation", func(args []string) error {
 		if len(args) != 1 {
 			return commandHandlerError("instantiated requires exactly 1 argument")
 		}
@@ -60,9 +75,6 @@ func main() {
 			}
 		}
 
-		ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
-		defer stop()
-
 		if v, err := nixbuild.EvalInstantiated(ctx, installable); err != nil {
 			return commandHandlerError(fmt.Sprintf("cannot evaluate for instantiated derivations: %v", err))
 		} else if flagJSON {