fix: update core cache correctly

Author: Luca Bianconi

Diff for: legacy/builder/phases/core_builder.go

@@ -95,7 +95,8 @@ func compileCore(ctx *types.Context, buildPath *paths.Path, buildCachePath *path
 	if buildCachePath != nil {
 		archivedCoreName := GetCachedCoreArchiveDirName(buildProperties.Get(constants.BUILD_PROPERTIES_FQBN),
 			buildProperties.Get("compiler.optimization_flags"), realCoreFolder)
-		targetArchivedCore = buildCachePath.Join(archivedCoreName).Join("core.a")
+		buildcache.GetOrCreate(buildCachePath, archivedCoreName)
+		targetArchivedCore = buildCachePath.Join(archivedCoreName, "core.a")
 		canUseArchivedCore := !ctx.OnlyUpdateCompilationDatabase &&
 			!ctx.Clean &&
 			!builder_utils.CoreOrReferencedCoreHasChanged(realCoreFolder, targetCoreFolder, targetArchivedCore)
@@ -121,11 +122,7 @@ func compileCore(ctx *types.Context, buildPath *paths.Path, buildCachePath *path
 
 	// archive core.a
 	if targetArchivedCore != nil && !ctx.OnlyUpdateCompilationDatabase {
-		if err := targetArchivedCore.Parent().Mkdir(); err != nil {
-			return nil, nil, fmt.Errorf(tr("creating core cache folder: %s", err))
-		}
 		err := archiveFile.CopyTo(targetArchivedCore)
-		buildcache.GetOrCreate(targetArchivedCore.Parent().Parent(), targetArchivedCore.Parent().Base())
 		if ctx.Verbose {
 			if err == nil {
 				ctx.Info(tr("Archiving built core (caching) in: %[1]s", targetArchivedCore))