README: clarify how to debug on CI services

README.md

@@ -204,14 +204,18 @@ In situations where the cache contains broken build artifacts, it can be necessa
 Debugging
 ---------
 
-You can run the server manually in foreground mode by running `SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache`, and send logging to stderr by setting the [`SCCACHE_LOG` environment variable](https://docs.rs/env_logger/0.7.1/env_logger/#enabling-logging) for example
-
-    SCCACHE_LOG=debug SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache
-
-Alternately, you can set the `SCCACHE_ERROR_LOG` environment variable to a path and set `SCCACHE_LOG` to get the server process to redirect its logging there (including the output of unhandled panics, since the server sets `RUST_BACKTRACE=1` internally).
+You can set the `SCCACHE_ERROR_LOG` environment variable to a path and set `SCCACHE_LOG` to get the server process to redirect its logging there (including the output of unhandled panics, since the server sets `RUST_BACKTRACE=1` internally).
 
     SCCACHE_ERROR_LOG=/tmp/sccache_log.txt SCCACHE_LOG=debug sccache
 
+You can also set these environment variables for your build system, for example
+
+    SCCACHE_ERROR_LOG=/tmp/sccache_log.txt SCCACHE_LOG=debug cmake --build /path/to/cmake/build/directory
+
+Alternatively, if you are compiling locally, you can run the server manually in foreground mode by running `SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache`, and send logging to stderr by setting the [`SCCACHE_LOG` environment variable](https://docs.rs/env_logger/0.7.1/env_logger/#enabling-logging) for example. This method is not suitable for CI services because you need to compile in another shell at the same time.
+
+    SCCACHE_LOG=debug SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache
+
 ---
 
 Interaction with GNU `make` jobserver