If you want to use Tencent Cloud Object Storage (aka COS) for the sccache cache, you need to set the SCCACHE_COS_BUCKET environment variable to the name of the COS bucket to use.
You must specify the endpoint URL using the SCCACHE_COS_ENDPOINT environment variable. More details are at COS endpoints.
You can also define a prefix that will be prepended to the keys of all cache objects created and read within the COS bucket, effectively creating a scope. To do that use the SCCACHE_COS_KEY_PREFIX environment variable. This can be useful when sharing a bucket with another application.
Sccache is able to load credentials from environment variables: TENCENTCLOUD_SECRET_ID and TENCENTCLOUD_SECRET_KEY. More details about the access of COS bucket can be found at the introduction page.