Rather, compared to Golang, why is pure Golang fast to build (in the matter of seconds), despite compiled?
Actually, any libraries in any languages (e.g. Python, Node.js, R, LaTeX, even Golang), that involves binding for C or C++, can be excruciating slow to compile, if not bundled with binary or precompiled. (I have seen an R library built in 20 minutes. Also, ConTeXt is very slow to build.)
go-sqlite3 when changing tags or CGO_CFLAGS even a little bit, will be slow to compile (in a matter of a few minutes).
And, not only C and C++. Java and Scala, amongst compiled languages, can be very slow to compiled as well.