memblock tests: Fix testing with 32-bit physical addresses

Building memblock simulator on x86_64 with 32BIT_PHYS_ADDR_T=1
produces "cast to pointer from integer of different size" warnings.
Fix them by building the binary in 32-bit environment when using
32-bit physical addresses.

Signed-off-by: Karolina Drobnik <karolinadrobnik@gmail.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>