tests: improve code coverage support

Fix the exclusion path for lcov; it should exclude the directory
with source code, not object files.

Use the COV environment variable to
* control whether we build for coverage or not
* select the output directory

Add a separate target for generating the report, so we can get a
report for all of the tests together or just a single test.

Add documentation.

Signed-off-by: Paul Fagerburg <pfagerburg@google.com>
Change-Id: I2bd2bfdedfab291aabeaa968c10b17e9b61c9c0a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54072
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>

0 files changed, 0 insertions, 0 deletions