two tests fail for 6.1.2 on RISC-V rc64imafdc FreeBSD

[Dennis Clarke]

>> ../../../gmp-6.1.2/test-driver: ./t-cmp_z: Exec format error
>> FAIL t-cmp_z (exit status: 126)
> 
> Since the format of the generated binary is incorrect, that's
> probably a compiler or linker bug. What "file reuse" says?
> Try also things like "nm reuse". Is this reproducible?
> 

That entire environment is unstable. Experimental at best.

I will see what I can do.

Dennis