R4R: Infrastructure for reproducible builds

[alessio]

This change set introduces support for building gaia with gitian
on the following GOOS/GOARCH pairs:

• darwin/386
• darwin/amd64
• linux/386
• linux/amd64
• linux/arm
• linux/arm64
• windows/386
• windows/amd64

cmd/gaia/contrib/gitian-descriptors/ contains gitian descriptor files.

cmd/gaia/contrib/gitian-keys/ contains:

• a keys.txt file that is meant to list core developers and gitian builders PGP keys.
• README.me to provide instructions on how to import the keys into one's
  personal GPG keyring.

The gosum utility is removed, so is the go.sum hashsum bit from gaiacli/gaiad
version string. It was meant to be a provisional mitigation to the lack of a
reproducible build process.

GOBIN is removed from all Makefiles. When GOBIN is set, go refuses to cross-compiles
binaries for foreign architectures. export GOBIN=$GOPATH/bin is unnecessary anyway
as by default go install places built binaries in $GOPATH/bin. Developers are required
to update their enviornment files and replace $GOBIN with $GOPATH/bin in PATH.

circleci configuration file is amended accordingly.

Instructions at https://github.com/cosmos/cosmos-sdk/wiki/Reproducible-builds

Closes: #4027
Closes: #4280

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #4262 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4262   +/-   ##
======================================
  Coverage    59.1%   59.1%           
======================================
  Files         217     217           
  Lines       14595   14595           
======================================
  Hits         8627    8627           
  Misses       5330    5330           
  Partials      638     638

[alessio]

Bnaries are now built with CGO enabled. I've successfully tested ledger support on Linux amd64.

[liamsi]

If I run ./cmd/gaia/contrib/gitian-build.sh on macosx, I get a ./cmd/gaia/contrib/gitian-build.sh: line 196: 1: unbound variable. Update: OK, I see this needs a param passed in, e.g. ./cmd/gaia/contrib/gitian-build.sh linux pwd.

Now:

Start the build
bin/gbuild:252:in ``': No such file or directory - sha256sum (Errno::ENOENT)
        from bin/gbuild:252:in `<main>'

OK, looks like coreutils installation failed. NVM.

[liamsi]

The instructions should probably contain a sentence on how to verify that the build I've created matches the official build / I successfully reproduced it.

[alessio]

@liamsi dixit:

The instructions should probably contain a sentence on how to verify that the build I've created matches the official build / I successfully reproduced it.

I will certainly do! And I will include instructions on how to retrieve and import builder keys into your GPG keyring, etc.

[liamsi]

Update: coreutils wasn't in PATH ... NVM

I ran git pull to get the latest changes (and deleted the gaia.sigs and the gitian-build-linux dirs, and restarted the build (via ./cmd/gaia/contrib/gitian-build.sh -s Ismail.Khoffi@gmail.com linux `pwd`) and got:

Updating apt-get repository (log in var/install.log)
Installing additional packages (log in var/install.log)
Upgrading system, may take a while (log in var/install.log)
Creating package manifest
Creating build script (var/build-script)
date: illegal time format
usage: date [-jnRu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ... 
            [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]
bin/gbuild:147:in `block (2 levels) in build_one_configuration': error looking up author date in cosmos-sdk (RuntimeError)
        from bin/gbuild:143:in `each'
        from bin/gbuild:143:in `block in build_one_configuration'
        from bin/gbuild:127:in `open'
        from bin/gbuild:127:in `build_one_configuration'
        from bin/gbuild:309:in `block (2 levels) in <main>'
        from bin/gbuild:304:in `each'
        from bin/gbuild:304:in `block in <main>'
        from bin/gbuild:302:in `each'
        from bin/gbuild:302:in `<main>'

[liamsi]

Build reports: https://github.com/Liamsi/gaia.sigs

[jackzampolin]

Builds the darwin for me!!