symbol 'sin'. cmd/link also processes the cgo_ldflag directives, so that it
knows that the eventual host link command must include the -lm
argument, so that the host linker will be able to find 'sin' in the
math library.

cmd/link Command Line Interface

The go command and any other Go-aware build systems invoke cmd/link
to link a collection of packages into a single binary. By default, cmd/link will