Are you talking in general, or bazel specifically?

Because in general yes, I agree, it would be nice. Probably not in source control though -- putting in compilers + libraries will make checkouts very slow, git is not really designed for tens of gigabytes of stuff.

For bazel specifically, this is not really well supported. The default rules and all examples just trust system-installed compilers.

There is ongoing work on building in docker (with all the corresponding security issues), and there are rumors that Google internal version has some sort of magic, but this is not a "mainstream" configuration.