Re-enable Windows builds

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-webservice.

I've rerendered the recipe as instructed in #32.

Here's a checklist to do before merging.

• [x] Bump the build number if needed. (not needed since other platforms recently rebuilt)

Fixes #32, #20, #27

[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.

[mbargull]

@conda-forge-admin, please rerender

[mbargull]

@conda-forge-admin, please rerender

[mbargull]

@conda-forge-admin, please rerender

[github-actions[bot]]

Hi! This is the friendly automated conda-forge-webservice.

I tried to rerender for you, but it looks like there was nothing to do.

This message was generated by GitHub actions workflow run https://github.com/conda-forge/r-xml-feedstock/actions/runs/3273478977.

[mbargull]

The reason why the Windows builds were not working since gh-19 was essentially a missing dependency. Prior to gh-19, it linked to m2w64-libxml2 which gets indirectly pulled in via r-base but is not declare as a direct depedency (instead of libxml2). By the time gh-19 got around, there was a change at https://github.com/conda-forge/libxml2-feedstock/pull/54 which lead to libxml2's xml2.lib being picked up instead of m2w64-libxml2's one (which caused the observed linking failures).

The Makevars.* change is needed so that it can find libxml2's headers. It only worked without it before because it took the headers from libxml2 but then the compiled library from m2w64-libxml2. With the added change we avoid that mix-and-match and also don't need the additional libxml2 dependency.

cc @jdblischak, @izahn

[mbargull]

@conda-forge-admin, please rerender

[jdblischak]

@mbargull Thanks for fixing this and providing a thorough explanation. Much appreciated!