You should always be able to build a Go 1.x compiler with just the 1.4 tool chain binaries. We have committed to sticking to the Go 1.4 language and libraries for the compiler tool chain.

Usually you don't keep the chain. You just keep a working compiler. You can also bootstrap from another implementation of the language, e.g., gccgo.

A common trick is to keep a highly portable interpreted version of the target language and then use this for bootstrapping, but often you attack new architectures by cross-compilation instead. It all depends.

Also, it is common for self-hosting languages to require themselves to build.