Port build config changes about C++ standard from Hive

**User Story**

https://gitlab.syncad.com/hive/hive/-/merge_requests/208

**Impacts**
Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.
- [ ] API (the application programming interface)
- [x] Build (the build process or something prior to compiled code)
- [ ] CLI (the command line wallet)
- [ ] Deployment (the deployment process after building such as Docker, Travis, etc.)
- [ ] DEX (the Decentralized EXchange, market engine, etc.)
- [ ] P2P (the peer-to-peer network for transaction/block propagation)
- [ ] Performance (system or user efficiency, etc.)
- [ ] Protocol (the blockchain logic, consensus, validation, etc.)
- [ ] Security (the security of system or user data, etc.)
- [ ] UX (the User Experience)
- [ ] Other (please add below)

**Additional Context (optional)**
Add any other context about your request here.

## CORE TEAM TASK LIST
- [ ] Evaluate / Prioritize Feature Request
- [ ] Refine User Stories / Requirements
- [ ] Define Test Cases
- [ ] Design / Develop Solution
- [ ] Perform QA/Testing
- [ ] Update Documentation

Start by reading the linked Hive merge request 208 and comparing its C++ standard build changes with BitShares Core's build configuration. Identify the corresponding configuration entry points in this repository, apply the equivalent change, and verify that the project still builds successfully.

Written by the indexing model from the issue text.