Re-arrange Windows R layout to be the same as Unix

[mingwandroid]

This is so that we can share noarch packages directly.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipe) and found some lint.

Here's what I've got...

For recipe:

• Jinja2 variable definitions are suggested to take a {%<one space>set<one space><variable name><one space>=<one space><expression><one space>%} form. See lines [2]

[mingwandroid]

@isuruf, @johanneskoester, @ocefpaf, @sodre, @bgruening please review.

[isuruf]

Will the already built R packages work with this change?

[mingwandroid]

No. They need to be rebuilt but we pin the r-base dependency exactly anyway. Need to rebuild the whole set. Probably best at 3.5 release time?

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[ocefpaf]

Need to rebuild the whole set. Probably best at 3.5 release time?

Yep. Let's do this for R 3.5.0 then.

[jakirkham]

cc @jdblischak

[jdblischak]

A few quick notes:

1. This build failed on Windows because we haven't successfully built R 3.4.1 for Windows since build number 1. If you look at the CI builds for R packages, r-base-3.4.1-3 is installed on Travis and CircleCI, but r-base-3.4.1-1 is installed on AppVeyor. See Unable to update pins for R 3.4.1 on win-64 #40
2. If we change the installation path for Windows, we'll need to update all the GPL'd packages that include the Windows-specific path to the GPL license files
3. The original plan was to wait until R 3.5.1 (to be released in late June) to build a new r-base package for conda-forge. Due to limitations in CI (and human) resources, we aim to support one version per minor release, and the x.x.1 allows for the first round of bug fixes after a new minor release

[jdblischak]

R 3.5.1 will be released on July 2

https://stat.ethz.ch/pipermail/r-announce/2018/000629.html

[jdblischak]

The Windows build has been fixed (the URL to download MiKTeK was broken; see #40 and #44).

@mingwandroid Would you be able to rebase your commits onto master? Note that you'll get a merge conflict because I also fixed the spacing in the Jinja2 variables defined in meta.yaml. If you'd prefer, I can perform the rebase and open a new PR (either on your branch or in the main repo).

[mingwandroid]

I would say things might be a little WIP at present (I'm adding openblas for macOS) but I rebased all my work on top of the master branch, here's a PR for discussion anyway: #45

[jdblischak]

Thanks @mingwandroid! I was referring to rebasing only the small number of commits in this PR, but comparing all the changes that have been made to the defaults r-base is also useful.

I created a new Issue to coordinate all the updates that need to be made the conda-forge r-base feedstock. Please share your thoughts in #46. Thanks!

[jdblischak]

R 3.5.1 has been released (release notes)

[bgruening]

@jdblischak #48

[bgruening]

@mingwandroid is working on a new iteration of this PR for 3.5.1