build: don't remove BUILD_LOG_DIR in _clean

targetclean should not remove BUILD_LOG

Fixes: db34b93331e9 (add a version that can be bumped to force toolchain/target rebuild)
Signed-off-by: Huangbin Zhan <[email protected]>

Makefile

@@ -51,7 +51,7 @@ printdb:
 prepare: $(target/stamp-compile)
 
 _clean: FORCE
-	rm -rf $(BUILD_DIR) $(STAGING_DIR) $(BIN_DIR) $(OUTPUT_DIR)/packages/$(ARCH_PACKAGES) $(BUILD_LOG_DIR) $(TOPDIR)/staging_dir/packages
+	rm -rf $(BUILD_DIR) $(STAGING_DIR) $(BIN_DIR) $(OUTPUT_DIR)/packages/$(ARCH_PACKAGES) $(TOPDIR)/staging_dir/packages
 
 clean: _clean
 	rm -rf $(BUILD_LOG_DIR)