travis.yml: Move the -fsanitize=thread testing to the gitlab-CI

Use clang-10, so we can also use the --enable-tsan configure
option instead of only passing the flag via --extra-cflags.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210211045455.456371-6-thuth@redhat.com>
Message-Id: <20210211122750.22645-6-alex.bennee@linaro.org>