Since [1], we have caused 'make lint' (or any recipes that list 'lint'
as a prerequisite) to fail if Git LFS imports non-standard packages
outside of its vendor tree.

However, this approach is deficient in that it does not correctly report
whether there are improperly vendored dependencies, since the pipeline
ends with "|| exit 0".

To prepare for a change in the invocation of "go list", let's make sure
that a final "grep ." fails (i.e., that the output of the pipeline up
until that point is empty) by adding a final "grep ." and negating the
exit code of the entire pipeline.

[1]: a1305a8 (Makefile: replace script/{fmt,lint} with '{fmt,lint}'
target, 2018-07-16)

Co-authored-by: brian m. carlson <bk2204@github.com>

Since we are now building on Go 1.11 (as of 074a2d4 (all: use Go 1.11
in CI, 2018-08-28)) and Go 1.11 supports Go Modules [1], let's stop
using Glide, and begin using Go Modules.

This involves a few things:

  * Teach the Makefile how to build go.sum files instead of glide.lock
    files.

  * Teach continuous integration services to build Git LFS in a
    non-$GOPATH environment, since (without setting GO111MODULE=on
    explicitly, which we choose not to do), this will break compiling
    Git LFS, because Go 1.11 will ignore modules present in a Go
    checkout beneath $GOPATH.

  * In order to do the above, let's also make sure that we are
    un-setting $GOCACHE in the environment, as this causes Go to work
    without modules support [2].

  * Because we're no longer building in a `$GOPATH`-based location,
    let's instruct the CircleCI base image to archive the new location,
    too.

  * Similarly, teach the RPM spec to build in a non-$GOPATH location.

  * By contrast, since we use dh_golang to build git-lfs binaries on
    Debian, let's wait until the upstream dh_golang package is released
    with support for Go 1.11 module support explicitly. Therefore, force
    GO111MODULE to be on so that we can build a copy of Git LFS whose
    checkout is within a $GOPATH.

Although the go.mod versions match the glide.yaml ones, the diff
attached is large because Go Modules do not vendor `_test.go` files,
whereas Glide does.

[1]: https://golang.org/doc/go1.11#modules
[2]: `GOCACHE=on` will be deprecated in Go 1.12, so this change makes
     sense for that reason, too.

Co-authored-by: brian m. carlson <bk2204@github.com>

In 2235198 (Makefile: replace script/bootstrap with 'make', 'make all',
2018-07-19), the Makefile learned how to make binaries of git-lfs,
including invoking 'go generate' in order to generate the resource.syso,
necessary for building on Windows.

In the commit mentioned above, we taught the Makefile recipe for
'resource.syso' to 'go get' the necessary 'goversioninfo' binary before
building, if callers do not have it.

In Go 1.10.3 and earlier, this caused no change to the vendor directory
or glide.yaml file, and instead installed the project in '$GOPATH', and
built the binary in '$GOPATH/bin'.

Since we are on Go 1.11, now, and running 'go get' from inside a module
directory causes the module's go.mod (and thusly, the go.sum, too) to
change, let's make it the caller's responsibility to provide a valid
'goversioninfo' binary in '$PATH'.

This allows us to avoid the burden of cleaning up after ourselves when
running 'go get' from within a directory that is itself a Go module.