Add R builds for CentOS 8

builder/docker-compose.yml

@@ -56,6 +56,17 @@ services:
     image: r-builds:centos-7
     volumes:
       - ./integration/tmp:/tmp/output
+  centos-8:
+    command: ./build.sh
+    environment:
+      - R_VERSION=${R_VERSION}
+      - LOCAL_STORE=/tmp/output
+    build:
+      context: .
+      dockerfile: Dockerfile.centos-8
+    image: r-builds:centos-8
+    volumes:
+      - ./integration/tmp:/tmp/output
   opensuse-42:
     command: ./build.sh
     environment: