That actually looks to be close to what I'd like to see for the build system itself. The rules for "how to build" are declared in the top-level and then piped through later. It also appears to have very little in the way of hard-coded knowledge about C/C++ and extending it to also support things like latex pipelines, documentation builds, and more would be well-supported.
It doesn't support -B or -n make flags though. The percentage output is nice. However, it doesn't seem to support out-of-source builds (I sort of hacked bootstrap.sh to do the bootstrap successfully, but there's no further support to get a full build working). The code base looks clean, so maybe I can get a patch and convince the maintainer to accept out-of-source as an option.