Configuration.md - note logging env variables

[Andrej730]

Added SCCACHE_ERROR_LOG and SCCACHE_LOG env variables to general configuration docs, added a note about the possible need to restart the server (stumbled upon this trying to enable logging).

[Andrej730]

@sylvestre
hi! can you please take a look?

[sylvestre]

they are documented in:

sccache/README.md

Line 258 in 764daee

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).

too but why not

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.11%. Comparing base (764daee) to head (b34064b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2480      +/-   ##
==========================================
- Coverage   71.14%   71.11%   -0.03%     
==========================================
  Files          64       64              
  Lines       35207    35147      -60     
==========================================
- Hits        25047    24994      -53     
+ Misses      10160    10153       -7     

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[Andrej730]

Yeah, I've seen it, just wanted to make sure Configuration.md will have a comprehensive list of all available configs.