meson: print configuration summary()

Fixes #249
10 jobs for meson-summary in 5 minutes and 20 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #3896125
gst-macos-10.15
meson macos

00:00:48

passed #3896122
meson-mingw-w64-build

00:03:17

manual #3896126
docker windows 1809 allowed to fail manual
meson msys2
passed #3896120
meson-shared-build

00:03:37

passed #3896121
meson-static-build

00:03:41

passed #3896123
docker windows 1809
meson vs2017 amd64

00:01:44

passed #3896124
docker windows 1809
meson vs2017 x86

00:01:44

passed #3896119
mingw-build

00:04:22

passed #3896117
shared-build

00:05:20

passed #3896118
static-build

00:04:17