In ba0e7333, we merged riscv32 and riscv64 in configure.
However, meson does not treat them the same.  We need to merge
them here as well.

Fixes: ba0e7333
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20211116095042.335224-1-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>