Add support for AWS Nitro Enclave emulation

Description:

It's a new feature in 9.2.0

• https://wiki.qemu.org/ChangeLog/9.2#x86
• https://gitlab.com/qemu-project/qemu/-/blob/master/docs/system/i386/nitro-enclave.rst

Definitely a bit niche, but someone somewhere is bound to want it at some point. Arch tends to enable features like this when easily available. It's a single additional system dep on libcbor libcbor.so.

I've only build-tested it. Feel free to knock this on the head if you consider it too niche and and/or the additional (minuscule) dep is too much.

Additional info:

• package version(s): 9.2.0