Add better error handling to bootDexJar function

aosp/2876754 missed adding error handling to one of the places which
consumes the dex jar deapexed from prebuilt apexes. This CL ensures that
when we have multiple prebuilt apexes _without_ flagging, the hiddenapi
processing code emits a more descriptive error "Multiple deapxers..."
rather than a cryptic error "<module> does not provide a dex jar"

Test: m nothing --no-skip-soong-tests

Change-Id: I80849fa7cca17d724ac53c94bb353b169175ee28

java/hiddenapi.go

@@ -44,7 +44,8 @@ type hiddenAPI struct {
 	//
 	// This must be the path to the unencoded dex jar as the encoded dex jar indirectly depends on
 	// this file so using the encoded dex jar here would result in a cycle in the ninja rules.
-	bootDexJarPath OptionalDexJarPath
+	bootDexJarPath    OptionalDexJarPath
+	bootDexJarPathErr error
 
 	// The paths to the classes jars that contain classes and class members annotated with
 	// the UnsupportedAppUsage annotation that need to be extracted as part of the hidden API
@@ -56,7 +57,10 @@ type hiddenAPI struct {
 	uncompressDexState *bool
 }
 
-func (h *hiddenAPI) bootDexJar() OptionalDexJarPath {
+func (h *hiddenAPI) bootDexJar(ctx android.ModuleErrorfContext) OptionalDexJarPath {
+	if h.bootDexJarPathErr != nil {
+		ctx.ModuleErrorf(h.bootDexJarPathErr.Error())
+	}
 	return h.bootDexJarPath
 }
 
@@ -77,7 +81,7 @@ type hiddenAPIModule interface {
 }
 
 type hiddenAPIIntf interface {
-	bootDexJar() OptionalDexJarPath
+	bootDexJar(ctx android.ModuleErrorfContext) OptionalDexJarPath
 	classesJars() android.Paths
 	uncompressDex() *bool
 }
@@ -126,6 +130,11 @@ func (h *hiddenAPI) initHiddenAPI(ctx android.ModuleContext, dexJar OptionalDexJ
 	h.active = isModuleInBootClassPath(ctx, module)
 }
 
+// Store any error encountered during the initialization of hiddenapi structure (e.g. unflagged co-existing prebuilt apexes)
+func (h *hiddenAPI) initHiddenAPIError(err error) {
+	h.bootDexJarPathErr = err
+}
+
 func isModuleInBootClassPath(ctx android.BaseModuleContext, module android.Module) bool {
 	// Get the configured platform and apex boot jars.
 	nonApexBootJars := ctx.Config().NonApexBootJars()