Independent testing of Windows Experimental branch

Preparations are underway to land the aevri/win32_minimal branch, which will bring minimal win32 functionality.

Although as of opening the ticket, the code is not ready for review, a minimal use-case does work.

Try to spot early problems by having some folks independently test the installation instructions.

Here they are:

• First, build and install buildboxcommon using these instructions, be sure to use the win32_2 branch of 'https://gitlab.com/aevri/buildbox-common'.
• Next, build and install buildboxcasd by following the same steps for the win32_2 branch of 'https://gitlab.com/aevri/buildbox-casd'.
• Next, make sure the built buildbox-casd is on your %PATH%. Note that the installed buildbox-casd doesn't have the required libraries, run it from the build directory instead (until we fix the install script).
• Finally, follow these instructions for installing buildstream on windows, using the aevri/win32_minimal branch.

You should now be able to do this, in your checkout of the BuildStream repo:

cd doc\examples\first-project
bst build hello.bst
bst artifact checkout hello.bst --directory hello_checkout
dir hello_checkout

Note that buildbox-casd output may be interspersed with BuildStream output, logging is another thing to resolve.

We have some volunteers for this:

• @tpollard
• @traveltissues (https://gitlab.com/snippets/1902536)
  • install git, vcpkg, chocolatey
  • install buildbox-common deps
  • build and install buildbox-common
  • build and install buildbox-casd
  • install python/pip
  • build and install buildstream
  • verify buildstream features (https://gitlab.com/snippets/1903227)

Note that we have a central issue for tracking win32 porting.