Add support for building the Linux blktests [1] into a guest image.
Once booted the tests can be run with commands like this:
```shell
cd /usr/blktests/; NVMET_TRTYPES=tcp ./check nvme/062
```
1: https://github.com/osandov/blktests
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
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