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!
Since this will remove the leading whitespace, wouldn't it be better to drop the `-` and unindent the block so we know what the whitespace of the final file will be?  I know it's generated content, but I still think it probably ought to follow gofmt like the rest of the codebase.