jit: fix assertion in GDBJITRegistrationListener

[oltolm]

This fixes the assertion Second attempt to perform debug registration. which happens in GDBJITRegistrationListener. It happens on Linux if compiled in debug mode.

auto cache = ObjectCache::load(path);

This variable contains the code. A reference to it is added to the JIT compiler and then it is destroyed at the end of the function jit_compiler::add and the JIT compiler now has a reference to destroyed code.

I changed it to pass the ownership of the code to the JIT compiler.