Implement support to build bitcoind with cmake/ninja

Summary: As per title. this is starting to look liek something ! No supportfor the walletfor now.

Test Plan: Build bitcoind using ninja, then do IBD on testnet.

Reviewers: schancel, #bitcoin_abc

Reviewed By: schancel, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D815