composer+worker: make dnf-json path externally configurable

The default value is the installation path.

cmd/osbuild-composer/composer.go

@@ -74,6 +74,7 @@ func NewComposer(config *ComposerConfigFile, stateDir, cacheDir string) (*Compos
 	logrus.Infof("Loaded %d distros", len(c.distros.List()))
 
 	c.solver = dnfjson.NewBaseSolver(path.Join(c.cacheDir, "rpmmd"))
+	c.solver.SetDNFJSONPath(c.config.DNFJson)
 
 	var jobs jobqueue.JobQueue
 	if config.Worker.PGDatabase != "" {

cmd/osbuild-composer/config.go

@@ -17,6 +17,7 @@ type ComposerConfigFile struct {
 	SyslogServer string          `toml:"syslog_server" env:"SYSLOG_SERVER"`
 	LogLevel     string          `toml:"log_level"`
 	LogFormat    string          `toml:"log_format"`
+	DNFJson      string          `toml:"dnf-json"`
 }
 
 type KojiAPIConfig struct {
@@ -108,6 +109,7 @@ func GetDefaultConfig() *ComposerConfigFile {
 		},
 		LogLevel:  "info",
 		LogFormat: "text",
+		DNFJson:   "/usr/libexec/osbuild-composer/dnf-json",
 	}
 }