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!
There shouldn't really be any way that IAMSTATIC can be set but empty here but yes it probably makes sense to change it to match the other uses of this idiom.