Add unit test for prebuilt_* generation from PRODUCT_COPY_FILES

Test: m nothing --no-skip-soong-tests
Bug: 375053752
Change-Id: I86c7e36439966896928b5954093a9047a764752b
diff --git a/etc/prebuilt_etc.go b/etc/prebuilt_etc.go
index 47b391c..943ec81 100644
--- a/etc/prebuilt_etc.go
+++ b/etc/prebuilt_etc.go
@@ -88,7 +88,7 @@
 
 var PrepareForTestWithPrebuiltEtc = android.FixtureRegisterWithContext(RegisterPrebuiltEtcBuildComponents)
 
-type prebuiltEtcProperties struct {
+type PrebuiltEtcProperties struct {
 	// Source file of this prebuilt. Can reference a genrule type module with the ":module" syntax.
 	// Mutually exclusive with srcs.
 	Src proptools.Configurable[string] `android:"path,arch_variant,replace_instead_of_append"`
@@ -175,7 +175,7 @@
 	android.ModuleBase
 	android.DefaultableModuleBase
 
-	properties prebuiltEtcProperties
+	properties PrebuiltEtcProperties
 
 	// rootProperties is used to return the value of the InstallInRoot() method. Currently, only
 	// prebuilt_avb and prebuilt_root modules use this.
@@ -607,7 +607,7 @@
 
 	module.AddProperties(props...)
 	module.AddProperties(
-		&prebuiltEtcProperties{},
+		&PrebuiltEtcProperties{},
 		&prebuiltSubdirProperties{},
 	)