从Yocto honister3.4之后，Yocto中local.conf和bb文件中的append和append函数命名产生了变化。由原来的IMAGE_INSTALL_append += 变为了IMAGE_INSTALL:append = ，do_install_append()变为了do_install:append()。
新语法说明：
appending-and-prepending-override-style-syntax
语法变更记录：
override-syntax-changes
变更的原因：
There are some variables which do not use override syntax which include the suffix to variables in layer.conf files such as BBFILE_PATTERN, SRCREV_xxx where xxx is a name from SRC_URI and PREFERRED_VERSION_xxx. In particular, layer.conf suffixes may be the same as a DISTRO override causing some confusion. We do plan to try and improve consistency as these issues are identified.
有一些变量不使用覆盖语法，其中包括layer.conf文件中变量的后缀，例如
BBFILE_PATTERN、 SRCREV_xxx，其中xxx是来自SRC_URI和 PREFERRED_VERSION_xxx的名称。特别是，layer.conf后缀可能与DISTRO覆盖相同，从而导致一些混淆。 随着这些问题的确定，我们确实计划尝试提高一致性。
