Pin Lombok version

This is necessary to ensure that historical builds continue to work, and to
maintain binary reproducibility for historical builds.

Author: emlun

buildSrc/src/main/groovy/project-convention-lombok.gradle

@@ -2,3 +2,7 @@ plugins {
     id "java"
     id "io.freefair.lombok"
 }
+
+lombok {
+    version = "1.18.44"
+}