9999f891d1 bench: Avoid deprecated use of volatile += (MarcoFalke)
Pull request description:
Deprecated in C++20 according to https://eel.is/c++draft/expr.ass#6 .
```
bench/examples.cpp:16:13: warning: compound assignment with ‘volatile’-qualified left operand is deprecated [-Wvolatile]
16 | sum += sin(d);
| ~~~~^~~~~~~~~
```
While C++20 is currently unsupported, I don't see any downside to a minor fixup to an example benchmark. This will also make a hypothetical C++20 patch smaller.
ACKs for top commit:
fanquake:
ACK 9999f891d1
Tree-SHA512: ca7d660fa8eba347a4648408a8b97a0ecb8263a825da7abd59129d783058102581e05b273667989f95480436a66d5384bd1e92d9ae79408f5b30e2178935cc38
9977e1658c