ci: add CentOS 8 support; drop CentOS 7

Refs: #5040, #5087
Change-Id: Ia680fecc41d16d21d7b03f117a30a2966cf46679
diff --git a/.jenkins.d/10-build.sh b/.jenkins.d/10-build.sh
index ccbcc93..f5ef90a 100755
--- a/.jenkins.d/10-build.sh
+++ b/.jenkins.d/10-build.sh
@@ -1,10 +1,5 @@
 #!/usr/bin/env bash
-set -e
-
-JDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
-source "$JDIR"/util.sh
-
-set -x
+set -ex
 
 git submodule sync
 git submodule update --init