internal/pkg: job count in container environment

This exposes preferred job count to the container initial process.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/testdata/main.go

@@ -9,7 +9,9 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"slices"
+	"strconv"
 	"strings"
 
 	"hakurei.app/check"
@@ -21,6 +23,10 @@ func main() {
 	log.SetFlags(0)
 	log.SetPrefix("testtool: ")
 
+	environ := slices.DeleteFunc(slices.Clone(os.Environ()), func(s string) bool {
+		return s == "CURE_JOBS="+strconv.Itoa(runtime.NumCPU())
+	})
+
 	var hostNet, layers, promote bool
 	if len(os.Args) == 2 && os.Args[0] == "testtool" {
 		switch os.Args[1] {
@@ -48,15 +54,15 @@ func main() {
 
 	var overlayRoot bool
 	wantEnv := []string{"HAKUREI_TEST=1"}
-	if len(os.Environ()) == 2 {
+	if len(environ) == 2 {
 		overlayRoot = true
 		if !layers && !promote {
 			log.SetPrefix("testtool(overlay root): ")
 		}
 		wantEnv = []string{"HAKUREI_TEST=1", "HAKUREI_ROOT=1"}
 	}
-	if !slices.Equal(wantEnv, os.Environ()) {
-		log.Fatalf("Environ: %q, want %q", os.Environ(), wantEnv)
+	if !slices.Equal(wantEnv, environ) {
+		log.Fatalf("Environ: %q, want %q", environ, wantEnv)
 	}
 
 	var overlayWork bool