pkg/imagebuilder: expose BuiltInBuildArgs for downstream

Expose map BuiltInBuildArgs so downstream users like buildah can use it.

Signed-off-by: Aditya R <[email protected]>

dispatchers.go

@@ -22,6 +22,7 @@ import (
 	"github.com/containers/storage/pkg/regexp"
 	"github.com/openshift/imagebuilder/signal"
 	"github.com/openshift/imagebuilder/strslice"
+	"golang.org/x/exp/maps"
 )
 
 var (
@@ -42,6 +43,11 @@ var builtinBuildArgs = map[string]string{
 	"BUILDVARIANT":   localspec.Variant,
 }
 
+//  Exposes map of global built-in args with their respective populated values.
+func GetBuiltinBuildArgs() map[string]string {
+	return maps.Clone(builtinBuildArgs)
+}
+
 func init() {
 	if localspec.Variant != "" {
 		builtinBuildArgs["TARGETPLATFORM"] = builtinBuildArgs["TARGETPLATFORM"] + "/" + localspec.Variant