meson: add summary() if Meson version is new enough

4 jobs for orc-meson-summary in 6 minutes and 45 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #1583474
debian sid

00:00:50

passed #1583477
docker windows 1809
msys2

00:04:27

passed #1583475
docker windows 1809
vs2017 amd64

00:01:27

passed #1583476
docker windows 1809
vs2017 x86

00:01:26