Check libidn2 version before proceding with one of the tests.

A known issue in libidn2 causes one of the tests of a fake A-label
to fail.  The problem should be corrected in version 2.0.5 of
libidn2.
7 jobs for 139-tests-for-idna2008-libidn2-merge-v9_12 in 8 minutes and 28 seconds (queued for 1 minute and 9 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #6738
docker linux

00:00:21

 
  Build
passed build:debian:sid:amd64 #6739
docker linux

00:02:24

passed build:debian:sid:i386 #6740
docker linux

00:02:22

 
  Test
passed systemtest:debian:sid:amd64 #6746
docker linux

00:05:10

passed systemtest:debian:sid:i386 #6748
docker linux

00:04:55

passed unittest:debian:sid:amd64 #6741
docker linux

00:00:57

passed unittest:debian:sid:i386 #6744
docker linux

00:00:54