Add CentOS 8 CI build

We have had some issues building in RHEL 8, so lets set up a CentOS 8 CI
system to try and catch those issues earlier.

Author: omajid

.vsts.pipelines/builds/matrix.yml

@@ -29,6 +29,17 @@ jobs:
     matrix:
       Offline: { type: Offline}
 
+- template: ../jobs/ci-linux.yml
+  parameters:
+    job: centos8
+    imageName: mcr.microsoft.com/dotnet-buildtools/prereqs:centos-8-daa5116-20200325130212
+    reportPrebuiltLeaks: false
+    matrix:
+      Production: { generatePrebuiltBurndown: true, runUnitTests: true }
+      Online: { type: Online }
+      Offline: { type: Offline }
+      Offline Portable: { type: Offline Portable }
+
 - template: ../jobs/ci-linux.yml
   parameters:
     job: debian9