I am surprised by this statement, as it's generally as easy as xcode-select --install to install the CLT (or failing that, installing full-blown Xcode). Slightly up in the article there is mention of Lion, so maybe this is related.
Then there's the problem of libraries. You have to use homebrew or whatever to install libraries in /usr/local. Some libraries would conflict with the system though, so you have to fiddle with env variables to make the build system find it.
Overall, building on MacOS/Xcode is a frustrating experience. I ended up installing nixos and using its toolchain for my work...
brew install gcc@8
OSX requires binaries to be signed to give them tracing/debugging privileges (or you can use root). It would be nice if Apple made this less painful -- or rather, if they stopped making native development increasingly more painful with every OS release.
I'm quite glad random unsigned binaries don't have the right to unilaterally attach to (signed) processes, otherwise the signature would be moot.