[avisynthplus] Add new port

[wangqr]

Describe the pull request

• What does your PR fix? Fixes issue #
  This PR adds the AviSynth+ port. It does not fix any issue. AviSynth+ is a dependency of FFMS2, so it could be related to Add FFMS2 #684 and [New Port Request] ffms2.dll #9105.

• Which triplets are supported/not supported? Have you updated the CI baseline?
  I'm only able to test x64-windows triplet. I have not updated the CI baseline. AviSynth+ only officially support Windows, and has experimental support for linux.

• Does your PR follow the maintainer guide?
  Yes.

[wangqr]

Someone on slack told me that I should use Supports: in CONTROL to skip the package build on CI, but it seems that it is not correctly skipping, at least on x64-windows-static. Other CI failed due to other packages broken, or some reason I cannot understand (PowerShell exited with code '1'.). Let me know if I still need to edit the CI baseline, and which one of fail / ignore I should use

[LilyWangL]

/azp run

[wangqr]

Well, I see that the only CI issue is x64-windows-static. I have already marked it as not supported in https://github.com/wangqr/vcpkg/blob/add-avisynthplus/ports/avisynthplus/CONTROL#L5 . The upstream does not support building as static library, see AviSynth/AviSynthPlus#130 .

[LilyWangL]

@wangqr Thanks for your PR. Please use vcpkg_fail_port_install in portfile.cmake to description this port doesn't support some triplets. And please modify VCPKG_PATH/scripts/ci.baseline.txt to account for the build failures on unsupported triplets.

[wangqr]

See comments above.
I have already used vcpkg_check_linkage to early-fail the unsupported static build. Which one of fail / ignore / skip should I use for unsupported triplet in ci.baseline.txt? It looks like ignore is only for packages that are breaking other packages, and for the rest 2 I don't understand their use case from the description

[LilyWangL]

Please use vcpkg_fail_port_install in portfile.cmake to description this port doesn't support some triplets. It will remind other users when they installing this port like this:

Error: UWP builds are currently not supported.
This port does not currently support architecture: arm

[ras0219-msft]

LGTM, thanks for the PR!