update compiler version to clang-20

Author: VarunNagaraju

.circleci/config.yml

@@ -17,7 +17,7 @@ jobs:
             set -o xtrace
             UBUNTU_CODE_NAME="focal"
             BASE_BRANCH="8.4"
-            COMPILER_VERSION="17"
+            COMPILER_VERSION="20"
             BOOST_VERSION="1_77_0"
             BOOST_DIR="/home/circleci/my_boost"