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

@@ -31,7 +31,7 @@ var (
 var localspec = platforms.DefaultSpec()
 
 // https://docs.docker.com/engine/reference/builder/#automatic-platform-args-in-the-global-scope
-var builtinBuildArgs = map[string]string{
+var BuiltInBuildArgs = map[string]string{
 	"TARGETPLATFORM": localspec.OS + "/" + localspec.Architecture,
 	"TARGETOS":       localspec.OS,
 	"TARGETARCH":     localspec.Architecture,
@@ -44,8 +44,8 @@ var builtinBuildArgs = map[string]string{
 
 func init() {
 	if localspec.Variant != "" {
-		builtinBuildArgs["TARGETPLATFORM"] = builtinBuildArgs["TARGETPLATFORM"] + "/" + localspec.Variant
-		builtinBuildArgs["BUILDPLATFORM"] = builtinBuildArgs["BUILDPLATFORM"] + "/" + localspec.Variant
+		BuiltInBuildArgs["TARGETPLATFORM"] = BuiltInBuildArgs["TARGETPLATFORM"] + "/" + localspec.Variant
+		BuiltInBuildArgs["BUILDPLATFORM"] = BuiltInBuildArgs["BUILDPLATFORM"] + "/" + localspec.Variant
 	}
 }
 
@@ -224,7 +224,7 @@ func from(b *Builder, args []string, attributes map[string]bool, flagArgs []stri
 	for n, v := range b.HeadingArgs {
 		argStrs = append(argStrs, n+"="+v)
 	}
-	defaultArgs := envMapAsSlice(builtinBuildArgs)
+	defaultArgs := envMapAsSlice(BuiltInBuildArgs)
 	filteredUserArgs := make(map[string]string)
 	for k, v := range b.UserArgs {
 		for _, a := range b.GlobalAllowedArgs {
@@ -634,7 +634,7 @@ func arg(b *Builder, args []string, attributes map[string]bool, flagArgs []strin
 					b.Args["TARGETPLATFORM"] = b.Args["TARGETPLATFORM"] + "/" + p.Variant
 				}
 			}
-		} else if val, ok := builtinBuildArgs[arg]; ok {
+		} else if val, ok := BuiltInBuildArgs[arg]; ok {
 			name = arg
 			value = val
 			hasDefault = true