util/testing: combine code coverage data

As part of the `what-jenkins-does` target, combine the code coverage
data from all unit tests (currently just coreboot and libpayload).

BUG=b:203800199
TEST=`make what-jenkins-does && ls -l coreboot-builds/coverage.info`

Signed-off-by: Paul Fagerburg <pfagerburg@google.com>
Change-Id: Id99615ca8279f80a402d5371221b8fd36fb91d55
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59959
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <patrick@coreboot.org>
diff --git a/util/testing/Makefile.inc b/util/testing/Makefile.inc
index 1411c7e..0830aea 100644
--- a/util/testing/Makefile.inc
+++ b/util/testing/Makefile.inc
@@ -105,6 +105,7 @@
 	$(MAKE) unit-tests JUNIT_OUTPUT=y COV=1
 	(cd payloads/libpayload; unset COREBOOT_BUILD_DIR; $(MAKE) unit-tests coverage-report JUNIT_OUTPUT=y COV=1)
 	$(MAKE) coverage-report JUNIT_OUTPUT=y COV=1
+	find . -name 'tests.info' -exec cat {} + >$(COREBOOT_BUILD_DIR)/coverage.info
 
 test-basic: test-lint test-tools test-abuild test-payloads test-cleanup