https://github.com/mozilla/sccache/pull/1280 adds support for using sccache when rustc is wrapped by another command, e.g /path/to/wrapper rustc.
This allows cargo users to use sccache as a rustc wrapper, and use another tool as a rustc wrapper for workspace members, resulting in commands like sccache /path/to/workspace/wrapper rustc.
This issue tracks the fact that running rustc with a wrapper is only supported by sccache when run under cargo (and hence the CARGO environment variable is defined). If a similar approach is taken by other build systems then sccache will fail to detect the compiler.
