Disable valgrind tests on arches which don't have valgrind
Some architectures (like riscv64) don't have valgrind at all. Make
sure the valgrind tests are completely disabled on these arches.
Signed-off-by: David Abdurachmanov <davidlt@rivosinc.com>
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>