fix centos-7setup

Author: craigcomstock

ci/fix-buildhost.sh

@@ -1,11 +1,13 @@
 #!/usr/bin/env bash
+# it is expected that this file is sourced, not executed directly
 set -ex
-thisdir="$(dirname "$0")"
+my_path="$(realpath "${BASH_SOURCE[0]}")"
+my_dir="$(dirbname "$my_path")"
 
 if [ -f /etc/os-release ]; then
   source /etc/os-release
   if [ "$ID" = "centos" ] && [ "$VERSION_ID" = "7" ]; then
-    source "$thisdir"/centos-7-setup-devtoolset-11.sh
+    source "$my_dir"/centos-7-setup-devtoolset-11.sh
   fi
 fi