Place sanitizers log into their own directory
This diff will make the sanitizers to output to a log file rather than
stderr, which has some advantages:
- This will prevent unrelated failures in functional tests, as some
assertion are checking the stderr output;
- This will allow for pushing the log files to the artifact list;
- This will make it easier to debug the failures, as related things
are kept together.
As a disadvantage when a sanitizer throw an error it will output nothing
to the console but still fail, creating a "failure for no visible
reason" output. This is mitigated by printing the log file after the tests if
Test Plan: See teamcity output, or reproduce locally with the same options.
Reviewers: #bitcoin_abc, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D3651