ci: survive the negative branch counters gcov reports

The coverage job fails while gcovr reads the data for triton.c:

    Unrecognized GCOV output ... branch  2 taken -1
    NegativeHits: Got negative hit value in gcov line 'branch  2 taken -1'

gcov emits those now and then, it is gcc bug 68080 and not something the
source can avoid. gcovr 6 and later treat it as a fatal parse error
unless --gcov-ignore-parse-errors names the case to tolerate.

Passing that option unconditionally is not enough, since the job runs on
both ubuntu-24.04 and ubuntu-22.04 and the gcovr in the latter predates
it and takes no value. Ask gcovr whether it knows the option before
adding it, and print what was decided so the log says which one ran.

0 files changed, 0 insertions, 0 deletions