go: support recompiling the standard library

[tdyas]

Some use cases for go require support for recompiling the standard library. For example, the compiler option added for fuzz testing (as described in #16609) is applied to the whole standard library as well as the user code. There is no pre-built package archives for that case like there are for the race detector case.

See https://github.com/golang/go/blob/0b2ad1d815ea8967c49b32d848b2992d0c588d88/src/cmd/go/internal/test/test.go#L791-L813 for an example in the fuzz case of go test enabling "fuzz instrumentation" of packages including standard library packages (with the exclusions listed in that code snippet).

A solution for this issue would solve the fuzz use case but also cross-compiling the standard library for other platforms.

[tdyas]

This is implemented as of #17914 landing on main which now always builds Go SDK packages from scratch without relying on the prebuilt package archives.