Ensure directories in the Soong output dir have appropriate permissions, so that 'm clean' works.

In particular, Bazel sometimes creates directories whose files cannot be deleted.

Test: m clean used to fail after b build //system/timezone/apex:com.android.tzdata, but now it works
Test: Added integration test which fails without this change

Change-Id: I08c8feed21c31ec187fe40be513f7eb4865c8ac3