cryptonight-pico doesn't work ... config parse error
If I use `cryptonight-pico` in the json config (as per Algorithm.cpp and STRATUM_EXT.md) then xmrig-proxy exists with an error saying

```
No valid configuration found. Exiting.
```

If I change `cryptonight-pico` to `cryptonight-lite` in the json then it starts, but it starts with "cn-lite/auto" instead of "cn-pico/trtl".

I see `#ifndef XMRIG_NO_CN_PICO` in https://github.com/xmrig/xmrig-proxy/blob/master/src/common/crypto/Algorithm.cpp#L87 ... and I didn't define that constant, so I'd expect cn-pico to be enabled.

Full config:

```
{
    "access-log-file": "/var/log/cn-turtle-access.log",
    "algo": "cryptonight-pico",
    "api": {
        "port": 0,
        "access-token": null,
        "id": null,
        "worker-id": null,
        "ipv6": false,
        "restricted": true
    },
    "background": false,
    "bind": [
        "0.0.0.0:5562",
        "[::]:5562"
    ],
    "colors": true,
    "custom-diff": 1000000,
    "donate-level": 0,
    "log-file": "/var/log/cn-turtle.log",
    "mode": "nicehash",
    "pools": [
        {
            "url": "pool.domain.com:1234",
            "user": "wallet_address",
            "pass": "x",
            "rig-id": null,
            "keepalive": true,
            "variant": "trtl",
            "tls": false,
            "tls-fingerprint": null
        }
    ],
    "retries": 100,
    "retry-pause": 3,
    "reuse-timeout": 0,
    "user-agent": null,
    "verbose": false,
    "debug": false,
    "watch": true,
    "workers": true
}
```
