Output bootclasspath_fragment's fragments property to sdk snapshot

Adds support for printing a PropertySet that has a property whose value
is an array of structs.

Bug: 179354495
Test: m nothing
      m conscrypt-module-sdk
      - check generated Android.bp file
Change-Id: I71be04188465610bcbea4d3c9a5e8204171a1eeb

java/bootclasspath_fragment.go

@@ -749,6 +749,9 @@ type bootclasspathFragmentSdkMemberProperties struct {
 	Stub_libs               []string
 	Core_platform_stub_libs []string
 
+	// Fragment properties
+	Fragments []ApexVariantReference
+
 	// Flag files by *hiddenAPIFlagFileCategory
 	Flag_files_by_category FlagFilesByCategory
 
@@ -789,6 +792,9 @@ func (b *bootclasspathFragmentSdkMemberProperties) PopulateFromVariant(ctx andro
 	// Copy stub_libs properties.
 	b.Stub_libs = module.properties.Api.Stub_libs
 	b.Core_platform_stub_libs = module.properties.Core_platform_api.Stub_libs
+
+	// Copy fragment properties.
+	b.Fragments = module.properties.Fragments
 }
 
 func (b *bootclasspathFragmentSdkMemberProperties) AddToPropertySet(ctx android.SdkMemberContext, propertySet android.BpPropertySet) {
@@ -811,6 +817,9 @@ func (b *bootclasspathFragmentSdkMemberProperties) AddToPropertySet(ctx android.
 		corePlatformApiPropertySet := propertySet.AddPropertySet("core_platform_api")
 		corePlatformApiPropertySet.AddPropertyWithTag("stub_libs", b.Core_platform_stub_libs, requiredMemberDependency)
 	}
+	if len(b.Fragments) > 0 {
+		propertySet.AddProperty("fragments", b.Fragments)
+	}
 
 	hiddenAPISet := propertySet.AddPropertySet("hidden_api")
 	hiddenAPIDir := "hiddenapi"