after consulting $GOROOT/pkg/$GOOS_$GOARCH.
	-S
		Print assembly and machine code.
	-V
		Print assembler version and exit.
	-debug
		Dump instructions as they are parsed.
	-dynlink
		Support references to Go symbols defined in other shared libraries.
	-e
		No limit on number of errors reported.
	-gensymabis
		Write symbol ABI information to output file. Don't assemble.
	-o file

must support both internal and external linking, depending on the
circumstances: if net is the only cgo-using package, then internal
linking is probably fine, but if other packages are involved, so that there
are dependencies on libraries beyond libc, external linking is likely
to work better. The compilation of a package records the relevant
information to support both linking modes, leaving the decision