CDRIVER-1991 Ensure we limit the hex to 7 digits

Author: bjori

.evergreen/config.yml

@@ -26,7 +26,7 @@ functions:
         working_dir: "mongoc"
         script: |
            if [ "${is_patch}" = "true" ]; then
-              VERSION=$(git describe)-patch-${version_id}
+              VERSION=$(git describe --abbrev=7)-patch-${version_id}
            else
               VERSION=latest
            fi