As the Gentoo chromium maintainer, not really - we strip most CFLAGS as part of the ebuild unless you enable a special USE flag to keep them and it’s not particularly supported - if you encounter breakage with that enabled the first thing I’m going to ask you to do is turn them off.
Edit: we do have some USE flags that control how the package is built, but that’s mostly choosing between the Google-bundled and system versions of libraries.
Edit the second: there isn’t a package on the binhost for chromium yet, I need to work out how to build it so that it isn’t an issue to distribute.