[pkg-go] Bug#798135: gb: FTBFS: insists on building with -m64

[Aaron M. Ucko]

Source: gb
Version: 0.1.0-1
Severity: important
Justification: fails to build from source

Builds of gb for 32-bit architectures (armel, armhf, and i386) all
failed because the compilation command lines in cgo.go specify -m64.
Please remove this option, since it is always either redundant or
inappropriate (depending on the architecture).

Thanks!