`distribute` script SSH key name is hard-coded

[mojomex]

The distribute script checks for an existing SSH key and generates one if none exists.
The proper way to do this would be to query info from the SSH agent (?) but currently
the key being looked up is id_rsa.pub:

sync_tooling/distribute

Line 12 in f1538de

if [ ! -f ~/.ssh/id_rsa.pub ]

This prevents other key types (ECDSA etc.) and keys with custom names from being recognized.
This should be implemented properly.