Add a flag for deploying without building

[vporton]

I deploy canisters this way:

dfx deploy pst --argument ...
dfx deploy CanDBIndex --argument ...
dfx deploy NacDBIndex --argument ...
#dfx deploy CanDBIndex
#dfx deploy pst
#dfx deploy payments
dfx deploy main

(I commented out deployment that is done by dfx.json dependencies instead of deploying by an explicit specifying the canister as deploy argument.)

Every deploy starts a build process that takes much time. Please, add a flag to deploy that will only deploy (without building) to speed-up this process.

[viviveevee]

dfx deploy is basically dfx canister create + dfx build + dfx canister install. If you just run dfx canister install on your own you get that functionality already