Change in coreboot[master]: tests: improve code coverage support

[Paul Fagerburg (Code Review)]

Attention is currently required from: Martin Roth, Jakub Czapiga, Paul Menzel, Julius Werner.
Hello build bot (Jenkins), Martin Roth, Jakub Czapiga, Julius Werner,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/54072

to look at the new patch set (#6).

Change subject: tests: improve code coverage support
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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 
Change-Id: I2bd2bfdedfab291aabeaa968c10b17e9b61c9c0a
---
A Documentation/technotes/2021-05-code-coverage.md
M Documentation/tutorial/part3.md
M Makefile
M tests/Makefile.inc
4 files changed, 104 insertions(+), 14 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/72/54072/6