This CL fix the bug that shouldCleanupRBELogsDir() never return true.
The way how shouldCleanupRBELogsDir() use to work is it will return true only if `RBE_proxy_log_dir` flag is not set.
But CI build always got this flag from gcl file, and developer build always got this flag set from ui/build/rbe.go (http://shortn/_K604iWNYkd). So there is never a case this shouldCleanupRBELogsDir() return true. That is to say, we never clean up
RBELogsDir by ourselves.
The reason why this is not a concern is that soong will automatically delete the out/soong/.temp folder every time when user run `m` or `lunch`, and the default RBELogsDir use to be `out/soong/.temp/rbe`. So soong is helping us to clean the logs before.
Previously, I merged this CL: https://r.android.com/3192211 to support running `lunch` in two terminals. In that CL, I moved the auto created RBELogsDir one level up to `out/soong/rbe`. This is causing a problem because RBELogsDir never get cleaned.
This CL will fix the shouldCleanupRBELogsDir() method, after this merged in, 1) if a user didn't set the `RBE_proxy_log_dir` flag, the logs in `out/soong/rbe` will be cleaned each time when running `m`, but `lunch` will not touch `out/soong/rbe`, so we still support running `lunch` in different terminals. 2) If user set `RBE_proxy_log_dir` flag to anything rather than `out/song/rbe`, the directory will not be cleaned by running `m`; 3) we have updated our doc everywhere that `out/soong/rbe` is re-client's default log dir, so I think it should be expected if user set `RBE_proxy_log_dir=out/soong/rbe`, then the logs will be deleted when next time `m` invoked, same as if they set `RBE_proxy_log_dir=out/soong/.temp/rbe` before.
Test: abtd run is green: http://shortn/_KqTvQelstP, local build with multiply lunch is not affected, and running m after a build can clean the out/soong/rbe directory.
Bug: 362798954
Change-Id: I38a7ad650fc59ad06716c5be7de6ecc61ead8eef
d9108d2d34