Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Introduce new `VolumeAttachment` API Object
**What this PR does / why we need it**:
Introduce a new `VolumeAttachment` API Object. This object will be used by the CSI volume plugin to enable external attachers (see design [here](https://github.com/kubernetes/community/pull/1258). In the future, existing volume plugins can be refactored to use this object as well.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: Part of issue https://github.com/kubernetes/features/issues/178
**Special notes for your reviewer**:
None
**Release note**:
```release-note
NONE
```
Introduce the v1alpha1 version to the Kubernetes storage API. And add a
new VolumeAttachment object to that version. This object will initially
be used only by the new CSI Volume Plugin. Eventually existing volume
plugins can be refactored to use it too.
Repro case:
$ make clean generated_files
$ hack/update-generated-protobuf.sh
This would complain about not finding `fmt`, and it was indicating the wrong
GOROOT. The problem was that the first step built binaries for generating
code, which *embeds* the value of GOROOT into the binary. The whole tree was
bind-mounted into the build container and then JUST the dockerized dir was
mounted over it. The in-container build tried to use the existing binaries,
but GOROOT is wrong.
This change whites-out the whole _output dir.
I first made just an anonymous volume for _output, but docker makes that as
root, which means I can't write to it from our non-root build. So I just put
it in the data container. This seems to work. The biggest change this makes
is that the $GOPATH/bin/ and $GOPATH/pkg/ dirs will persist across dockerized
builds.
This allows us to start building real dependencies into Makefile.
Leave old hack/* scripts in place but advise to use 'make'. There are a few
rules that call things like 'go run' or 'build/*' that I left as-is for now.