because bootStrap.groovy file is too big
The Java Virtual Machine has a limitation that methods cannot be larger than 64k (65536 bytes). This post describes this limitation in details.
The best way to overcome this issue is simply splitting your large method into smaller ones, which is generally a good practice.
Also notice that the JVM JIT compiler will not compile methods larger than 8K. You can however change this behavior using the -XX:-DontCompileHugeMethods option.