Stop using -X flag to set global variables

I'd like to build docker with gccgo, which does not have any version of go tool 6l's -X flag.  So this replaces the use of this flag with either code generation or build tags as appropriate.

I find make.sh and the bundles all fairly confusing, but I **think** this is correct.  "make test" passes at least!
Ah, I see now.  This was supposed to be `:=`, not just `=`. :smile: