…g for riscv

54ce4fa build: improve macro for testing -latomic requirement (fanquake)
2c010b9 add std::atomic include to bitcoin-util.cpp (fanquake)

Pull request description:

  Since the merge of bitcoin#19937, riscv builds have been failing, due to a link issue with [`std::atomic_exchange`](https://en.cppreference.com/w/cpp/atomic/atomic_exchange) in `bitcoin-util`:
  ```bash
    CXXLD    bitcoin-util
  bitcoin_util-bitcoin-util.o: In function `grind_task':
  /home/ubuntu/build/bitcoin/distsrc-riscv64-linux-gnu/src/bitcoin-util.cpp:98: undefined reference to `__atomic_exchange_1'
  collect2: error: ld returned 1 exit status

  ```

  We have a [macro](https://github.com/bitcoin/bitcoin/blob/master/build-aux/m4/l_atomic.m4) that tries to determine when `-latomic` is required, however it doesn't quite work well enough, as it's currently determining it isn't needed:
  ```bash
  ./autogen.sh
  ./configure --prefix=/home/ubuntu/bitcoin/depends/riscv64-linux-gnu
  ...
  checking whether std::atomic can be used without link library... yes
  ```

  This PR adds a call to `std::atomic_exchange` to the macro, which will get us properly linked against `-latomic` on riscv:
  ```bash
  checking whether std::atomic can be used without link library... no
  checking whether std::atomic needs -latomic... yes
  ```

  Also adds an `<atomic>` include to `bitcoin-util.cpp`.

ACKs for top commit:
  laanwj:
    Tested ACK 54ce4fa

Tree-SHA512: 963c875097ee96b131163ae8109bcf8fecf4451d20faa2f3d223f9938ea3d8d1ed5604e12ad82c2b4b1c605fd293a9b6b08fefc00dd3e68d09c49e95029c6f50

riscv builds are currently failing because -latomic isn't being linked
against, when it is needed:
```bash
/home/ubuntu/build/bitcoin/distsrc-riscv64-linux-gnu/src/bitcoin-util.cpp:98: undefined reference to `__atomic_exchange_1'
```

This exteneds our macro to ensure that -latomic is linked against when
required.

Github-Pull: bitcoin#20938
Rebased-From: 54ce4fa

c76e7b6 [Core] Fix data races in bls_worker and use ctpl_stl queue (Fuzzbawls)
55babf4 [Build] Improve std::atomic test macro (Fuzzbawls)

Pull request description:

  Coming from dashpay#4240, bitcoin#20938, and bitcoin#21920, this resolves numerous compile-time inconsistencies/failures on certain combos of gcc and cpu arch that were observed on launchpad.net over the 5.4.0 release cycle.

ACKs for top commit:
  furszy:
    ACK c76e7b6
  random-zebra:
    ACK c76e7b6

Tree-SHA512: d931142f978d0d22668b9ff2e16d48c148b7d163b35aeef149ab08a13174536c035f2581a8ec5bc9782226fcb27ed33b08aec475d1522d8e8532d00a12c5df72