Ledger support is disabled in make install

[tbruyelle]

The reproducible build feature has disabled CGO, but CGO is actually necessary for ledger support.

[tbruyelle]

Interestingly, ledger support is also disabled in gaia releases(*), because like govgen, CGO is disabled (CGO_ENABLED=0) in the goreleaser config. What reproducible build did is to disable CGO in Makefile, ensuring aligned LD_FLAGS between Makefile and goreleaser. So I rename the issue to "Ledger suppor is disabled from Makefile", because it has always been the case for the github binaries generated by goreleaser.

If we remove CGO_ENABLED=0 from the Makefile, we get ledger support from make install (because by default CGO is enabled) but we break reproducible builds.
If we set CGO_ENABLED=1 in both Makefile and goreleaser, we get ledger support but we probably also break reproducible builds as we introduce OS related stuff in the build process (this needs to be checked, but I'm pretty sure it is the case).

An other solution might be to add a new target make install-with-ledger, so we keep reproducible builds between make install and goreleaser, but we provide a way to build a binary with ledger support. I think that's the best solution.

(*) only recent releases of gaia has ledger support, since they had to enable CGO for cosmowasm.

[tbruyelle]

Fixed by #52 which introduces a build-ledger makefile target.