How to execute gradle with JDK 64bit, but run tests with JDK 32bit

I have a big project. It has more 400 submodules, therefore I really want to build it in parallel. However, build it in parallel with all available cores will require a lots of memory. Ideally, I should do that with a 64bit JDK to allocate maybe up to 16g memory for the building...

But some tests depend on 32bit native library. We need to run them with a 32 bit JRE..

Any idea to build the project with JDK 64 bit, but execute the tests with just 32bitJRE?

Many many thanks.