CI: added macOS build job.

7 jobs for ci-macos in 2 minutes and 51 seconds
Status Job ID Name Coverage
  Build
passed #1874
amd64 debian
build-debian

00:00:22

passed #1878
debian aarch64
build-debian-aarch64

00:01:17

passed #1879
debian clang5 aarch64
build-debian-aarch64-clang-5

00:00:42

passed #1875
amd64 debian
build-debian-static

00:00:23

passed #1880
macos
build-macos

00:00:09

passed #1876
win32
build-win32

00:00:22

passed #1877
win64
build-win64

00:00:24