Improve make -f docker.Makefile vendor

[simonferquel]

- What I did

Initial work from @ijc brought a containerized vendoring which was great but had a few issues:

• did not work on Windows: dependencies containing symlinks could not be written by golang/dep on a cifs-mounted volume (wich is the case when mounting a windows dir in Docker Desktop)
• slow: 2 reasons for that: doing the vendoring accross a cifs or osxfs bind mount was far from ideal due to FS latency and caching issues. There was no cache preservation between 2 calls.

This PR fixes those issues.

- How I did it

• Not using bind mounts: we resolve the vendoring directly in the container RootFS, then copy back the vendor dir and the Gopkg.lock file (which might have been updated) to the host
• Mounting a volume in which golang/dep will keep repo info and git clones in cache

Note that the dep-cache mount point and DEPCACHEDIR env var are //dep-cache and not /dep-cache. From a Unix FS point of view both paths are equivalent. But some windows shells (like the bash version shipped with Git on Windows) tries to do clever conversions to win32 paths when detecting unix-style paths in command line arguments, which makes docker trying to mount the volume in "c:\Program Files\Git\bin..." which makes no sense in a Linux container. Doubling the initial "/" disable this behavior.

- How to verify it

try make -f docker.Makefile on Windows

[simonferquel]

Yes, the exact reason why the target starts with an ugly docker rm -f docker-app-vendoring || echo "" I suppose I should also add a target for cleaning the vendoring cache volume (in case of a dep crash / an untimely docker rm -f). I'll add a commit with that.

[codecov[bot]]

Codecov Report

Merging #482 into master will decrease coverage by 0.12%. The diff coverage is 73.43%.

@@            Coverage Diff            @@
##           master    #482      +/-   ##
=========================================
- Coverage   69.53%   69.4%   -0.13%     
=========================================
  Files          51      50       -1     
  Lines        2629    2553      -76     
=========================================
- Hits         1828    1772      -56     
+ Misses        569     545      -24     
- Partials      232     236       +4

Impacted Files	Coverage Δ
internal/commands/inspect.go	78.37% <100%> (ø)	:arrow_up:
internal/commands/uninstall.go	65.78% <50%> (-2.79%)	:arrow_down:
internal/commands/status.go	71.42% <50%> (-3.58%)	:arrow_down:
internal/commands/install.go	63.63% <50%> (-1.45%)	:arrow_down:
internal/commands/upgrade.go	63.46% <70%> (-1.85%)	:arrow_down:
internal/commands/cnab.go	68.99% <80.48%> (-10.21%)	:arrow_down:
types/parameters/parameters.go	92.06% <0%> (-4.77%)	:arrow_down:
internal/store/store.go	71.42% <0%> (-0.58%)	:arrow_down:
internal/commands/dockerdesktop.go

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[ijc]

Urk, I don't know wtf is going on with how those comments are presented (I did a per-commit review in different tags, but normally that DTRT, although I may have accidentally clicked "single comment" once or twice). Anyway, I think all of my comments have been captured in some form above.

[simonferquel]

@ijc @thaJeztah, just updated the PR. PTAL. I kept using the double "//" as the MSYS_* env var does not apply to my current mingw make environment... Imerged create/start into a single run, and I added the possibility to pass arguments (usefull for things like -update golang/x/sys etc.)