Attempting to build RISC-V "minimal" variant fails with:

```
* For target hotspot_variant-minimal_libjvm_objs_macroAssembler_riscv.o:
In file included from /home/shade/trunks/jdk/src/hotspot/share/utilities/globalDefinitions.hpp:29,
                 from /home/shade/trunks/jdk/src/hotspot/share/memory/allocation.hpp:29,
                 from /home/shade/trunks/jdk/src/hotspot/share/memory/arena.hpp:28,
                 from /home/shade/trunks/jdk/src/hotspot/share/runtime/handles.hpp:28,
                 from /home/shade/trunks/jdk/src/hotspot/share/code/oopRecorder.hpp:28,
                 from /home/shade/trunks/jdk/src/hotspot/share/asm/codeBuffer.hpp:28,
                 from /home/shade/trunks/jdk/src/hotspot/share/asm/assembler.hpp:28,
                 from /home/shade/trunks/jdk/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp:28:
/home/shade/trunks/jdk/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp: In member function 'void MacroAssembler::movoop(Register, jobject)':
/home/shade/trunks/jdk/src/hotspot/cpu/riscv/macroAssembler_riscv.cpp:1966:30: error: invalid use of incomplete type 'class CollectedHeap'
 1966 | assert(Universe::heap()->is_in(JNIHandles::resolve(obj)), "should be real oop");
      | ^~

```