Fix some issues in bp2build converter for python_binary_host.

1) Bp2build convert python_binary_host main attribute as LabelAttribute. Currently "main" attribute in python_binary_host is handled as string but for some modules (e.g certify_bootimg) the "main" attribute points to a file in its subpackage like "subpackage/file.py" and should be converted to "//.../subpackage:file.py".

2) Filter out duplicated labels in the merged list of "required" attributes of python_binary_host and its defaults.

Test: b build //system/tools/mkbootimg:certify_bootimg
Test: b build //build/make/tools/releasetools:check_target_files_signatures
Bug: 253081249
Bug: 253101186

Change-Id: Ic2cb4cadec2c1348da70af9f0730da9914d3a8ca

python/binary.go

@@ -34,7 +34,7 @@ func registerPythonBinaryComponents(ctx android.RegistrationContext) {
 }
 
 type bazelPythonBinaryAttributes struct {
-	Main           *string
+	Main           *bazel.Label
 	Srcs           bazel.LabelListAttribute
 	Deps           bazel.LabelListAttribute
 	Python_version *string
@@ -42,17 +42,6 @@ type bazelPythonBinaryAttributes struct {
 }
 
 func pythonBinaryBp2Build(ctx android.TopDownMutatorContext, m *Module) {
-	var main *string
-	for _, propIntf := range m.GetProperties() {
-		if props, ok := propIntf.(*BinaryProperties); ok {
-			// main is optional.
-			if props.Main != nil {
-				main = props.Main
-				break
-			}
-		}
-	}
-
 	// TODO(b/182306917): this doesn't fully handle all nested props versioned
 	// by the python version, which would have been handled by the version split
 	// mutator. This is sufficient for very simple python_binary_host modules
@@ -72,13 +61,24 @@ func pythonBinaryBp2Build(ctx android.TopDownMutatorContext, m *Module) {
 
 	baseAttrs := m.makeArchVariantBaseAttributes(ctx)
 	attrs := &bazelPythonBinaryAttributes{
-		Main:           main,
+		Main:           nil,
 		Srcs:           baseAttrs.Srcs,
 		Deps:           baseAttrs.Deps,
 		Python_version: python_version,
 		Imports:        baseAttrs.Imports,
 	}
 
+	for _, propIntf := range m.GetProperties() {
+		if props, ok := propIntf.(*BinaryProperties); ok {
+			// main is optional.
+			if props.Main != nil {
+				main := android.BazelLabelForModuleSrcSingle(ctx, *props.Main)
+				attrs.Main = &main
+				break
+			}
+		}
+	}
+
 	props := bazel.BazelTargetModuleProperties{
 		// Use the native py_binary rule.
 		Rule_class: "py_binary",