test: Fix dlwrap on riscv64

[piggynl]

See sysdeps/unix/sysv/linux/riscv/rv64/libdl.abilist in glibc's source.

[andreabolognani]

Hi, can the maintainers please take a look at this patch?

I can't claim that I fully understand what it does, but I can confirm that applying it on top of 1.5.10 makes it possible to successfully build the Fedora package on riscv64.

The approach currently used on Fedora (where riscv64 is not yet an officially supported architecture) and Debian (where it already is) is to simply skip the test suite altogether, which is clearly not ideal. See the Fedora hack and the Debian one for reference.

There is a PR that is trying to get the patch added to the Fedora package: this is much more likely to move forward if the patch in question had already been accepted upstream. And of course we want a future upstream release to work out of the box.

Thanks in advance for your consideration!