Update on rtools4 and ucrt support

Hi Jeroen,

I mostly lurk on this list, but I was struck by your combative tone.

To pick on two random bits:
  

? a 6gb tarball with manually built things on his personal machine?

? a black-box system that is so opaque and complex that only one person
knows how it works, and would make it much more difficult for
students, universities, and other organisations to build R packages
and libraries on Windows?

Tomas? tool chain isn't a blackbox, it has copious documentation (see [1])
and builds on any machine thanks to the provided docker container.

This is not to criticise your work which has its unique strengths, but to
state the obvious: these strengths are best discussed without passion
based on factually accurate descriptions.

I agree with Jan.  I'm not sure a discussion in this forum would be 
fruitful, but I really wish Jeroen and Tomas would get together, aiming 
to merge their toolchains, keeping the best aspects of both.

I haven't been involved in the development of either one, but have been 
a "victim" of the two chain rivalry, because the rgl package is not easy 
to build.  I get instructions from each of them on how to do the build, 
and those instructions for one toolchain generally break the build on 
the other one.  While it is probably possible to detect the toolchain 
and have the build adapt to whichever one is in use, it would be a lot 
easier for me (and I imagine every other maintainer of a package using 
external libs) if I just had to follow one set of instructions.

Duncan Murdoch