gobuild: drop support for building on Go < 1.10 (#2960)
gobuild: drop support for building on Go < 1.10 (#2960)

Remove code to build on old versions of Go that didn't support the all=
query for -gcflags.
go-delve/delve,go-delve/delve,go-delve/delve,go-delve/delve,go-delve/delve