Added a new docker for ubuntu 20.04.
This docker has support for Thread Sanitizer
including one patch we need in one of the header files.
https://github.com/llvm/llvm-project/commit/a72dc86cd



This command will build with tsan enabled:
make docker-test-tsan-ubuntu2004 V=1

Also added the TSAN suppresion file to disable certain
cases of TSAN warnings.

Cc: Fam Zheng <fam@euphon.net>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Robert Foley <robert.foley@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200609200738.445-10-robert.foley@linaro.org>
Message-Id: <20200612190237.30436-13-alex.bennee@linaro.org>