Build requires C++14, CMake doesn't set it

What version of protobuf and what language are you using? Version: main Language: N/A

What operating system and version?

macOS Sonoma 14.3.1

What runtime / compiler are you using (e.g., python version or gcc version)

Apple clang version 15.0.0 (clang-1500.1.0.2.5)
Target: arm64-apple-darwin23.3.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

cmake version 3.28.3

What did you do?

Following the command from https://github.com/protocolbuffers/protobuf/blob/main/conformance/README.md:

$ cmake . -Dprotobuf_BUILD_CONFORMANCE=ON && cmake --build .

What did you expect to see

The conformance_test_runner binary is produced.

What did you see instead?

Many compilation errors, probably to do with not using -std=c++11.

Compilation output gist.