executor: resolve BultInArgs while expanding baseImage

While creating a dependency map, executor must consider expanding base
images with `builtInArgs` like `TARGETARCH, TARGETOS` etc so buildah can
still keep and use the stages as dependency later on.

Closes: #4820

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

Author: flouthoc

imagebuildah/executor.go

@@ -751,9 +751,11 @@ func (b *Executor) Build(ctx context.Context, stages imagebuilder.Stages) (image
 							}
 							headingArgs := argsMapToSlice(stage.Builder.HeadingArgs)
 							userArgs := argsMapToSlice(stage.Builder.Args)
+							populatedBuiltInBuildArgs := argsMapToSlice(imagebuilder.BuiltInBuildArgs)
 							// append heading args so if --build-arg key=value is not
 							// specified but default value is set in Containerfile
 							// via `ARG key=value` so default value can be used.
+							userArgs = append(userArgs, populatedBuiltInBuildArgs...)
 							userArgs = append(headingArgs, userArgs...)
 							baseWithArg, err := imagebuilder.ProcessWord(base, userArgs)
 							if err != nil {

tests/bud.bats

@@ -266,6 +266,10 @@ symlink(subdir)"
 
   run_buildah build --platform linux/$myarch/$myvariant $WITH_POLICY_JSON -t test -f $BUDFILES/base-with-arg/Containerfile
   expect_output --substring "This is built for $myarch"
+
+  # Should work without platform string as well
+  run_buildah build $WITH_POLICY_JSON -t test -f $BUDFILES/base-with-arg/Containerfile
+  expect_output --substring "This is built for $myarch"
 }
 
 @test "build with basename resolving user arg" {