在 build/core/ccache.mk 中有一段注释

We no longer provide a ccache prebuilt.

Ours was old, and had a number of issues that triggered non-reproducible

results and other failures. Newer ccache versions may fix some of those

issues, but at the large scale of our build servers, we weren’t seeing

significant performance gains from using ccache – you end up needing very

good locality and/or very large caches if you’re building many different

configurations.

Local no-change full rebuilds were showing better results, but why not just

use incremental builds at that point?

So if you still want to use ccache, continue setting USE_CCACHE, but also set

the CCACHE_EXEC environment variable to the path to your ccache executable.

大概意思是aosp中预置的ccache已经太老了，会引起一些意想不到的错误，不建议使用

如果一定要使用的话，可以自己安装最新版本的ccache，然后把ccache的路径添加到环境变量中

export CCACHE_EXEC := /usr/bin/ccache

export USE_CCACHE=true

不过这种方法我试了好像不起作用，可以直接在 build/core/ccache.mk 文件中添加

CCACHE_EXEC := /usr/bin/ccache