It looks like g++-9 and above (which is used in Github Actions) is incompatible with lcov-1.14, which is the latest release available on the Debian pool ftp site (see CI scripts). However, a new version of lcov, 1.15, has been released and is available via Github. See: https://github.com/linux-test-project/lcov/releases
See: https://github.com/linux-test-project/lcov/issues/58
It looks like g++-9 and above (which is used in Github Actions) is incompatible with lcov-1.14, which is the latest release available on the Debian pool ftp site (see CI scripts). However, a new version of lcov, 1.15, has been released and is available via Github. See: https://github.com/linux-test-project/lcov/releases