Handle filename variations for prebuilt_etc in bp2build

Bp2build now handles these cases:

-filename is specified as a property
-if filename is not specified and filename_from_src = true,
	filename is set as the src
-filename defaults to the module name otherwise

Bug: 228353188
Test: bp2build/prebuilt_etc_conversion_test.go
Change-Id: Ia4c9b2c89f100e4ed9363dc3ba20ea501b776216

etc/prebuilt_etc.go

@@ -670,10 +670,11 @@ func generatePrebuiltSnapshot(s snapshot.SnapshotSingleton, ctx android.Singleto
 // For Bazel / bp2build
 
 type bazelPrebuiltFileAttributes struct {
-	Src         bazel.LabelAttribute
-	Filename    string
-	Dir         string
-	Installable bazel.BoolAttribute
+	Src               bazel.LabelAttribute
+	Filename          bazel.LabelAttribute
+	Dir               string
+	Installable       bazel.BoolAttribute
+	Filename_from_src bazel.BoolAttribute
 }
 
 // ConvertWithBp2build performs bp2build conversion of PrebuiltEtc
@@ -694,8 +695,18 @@ func (module *PrebuiltEtc) ConvertWithBp2build(ctx android.TopDownMutatorContext
 	}
 
 	var filename string
-	if module.properties.Filename != nil {
-		filename = *module.properties.Filename
+	var filenameFromSrc bool
+	moduleProps := module.properties
+
+	if moduleProps.Filename != nil && *moduleProps.Filename != "" {
+		filename = *moduleProps.Filename
+	} else if moduleProps.Filename_from_src != nil && *moduleProps.Filename_from_src {
+		if moduleProps.Src != nil {
+			filename = *moduleProps.Src
+		}
+		filenameFromSrc = true
+	} else {
+		filename = ctx.ModuleName()
 	}
 
 	var dir = module.installDirBase
@@ -714,11 +725,16 @@ func (module *PrebuiltEtc) ConvertWithBp2build(ctx android.TopDownMutatorContext
 
 	attrs := &bazelPrebuiltFileAttributes{
 		Src:         src,
-		Filename:    filename,
 		Dir:         dir,
 		Installable: installable,
 	}
 
+	if filename != "" {
+		attrs.Filename = bazel.LabelAttribute{Value: &bazel.Label{Label: filename}}
+	} else if filenameFromSrc {
+		attrs.Filename_from_src = bazel.BoolAttribute{Value: moduleProps.Filename_from_src}
+	}
+
 	props := bazel.BazelTargetModuleProperties{
 		Rule_class:        "prebuilt_file",
 		Bzl_load_location: "//build/bazel/rules:prebuilt_file.bzl",