[libxml2] Update to 2.9.9

[myd7349]

Fix #5177

[myd7349]

I am tring to rewrite the port file with vcpkg_from_github: myd7349@31a7ea2.

1. libxml2 downloaded from ftp://xmlsoft.org/libxml2/libxml2-2.9.4.tar.gz or http://xmlsoft.org/sources/libxml2-2.9.4.tar.gz already contains xmlversion.h.

   After switching to vcpkg_from_github, we have to config xmlversion.h.in by ourselves.

2. libxml2 downloaded from ftp://xmlsoft.org/libxml2/libxml2-2.9.4.tar.gz or http://xmlsoft.org/sources/libxml2-2.9.4.tar.gz doesn't contain rngparser.c. And the build failed with this file. So I excluded this file from the sources list.

[myd7349]

A project for testing this port: https://github.com/myd7349/Ongoing-Study/tree/master/cpp/CMake/vcpkg/libxml2_test

[Codiferous]

@myd7349 Sorry for the delay in processing this PR. We're seeing failures in the CI with this change, but I don't think it's the fault of this PR. I believe something else is going on. It's taking some time to investigate the issues.

The issues we're seeing look exactly like the errors here on macOS. I haven't been able to find a uuid.h that collides with the system provided one, so we're still trying to figure out where the issue is coming from.

[myd7349]

@Codiferous Thanks for the reply! I didn't test it on Mac(Because I don't have a Mac book 😄).

[myd7349]

UWP support:

1. Failed to install liblzma on UWP: [liblzma] Fix for UWP build #5607

2. Link errors:

   Creating library E:/vcpkg/buildtrees/libxml2/x86-uwp-dbg/Debug/libxml2.lib and object E:/vcpkg/buildtrees/libxml2/x86-uwp-dbg/Debug/libxml2.exp
   4>catalog.obj : error LNK2019: unresolved external symbol _GetModuleHandleA@4 referenced in function _xmlInitializeCatalog [E:\vcpkg\buildtrees\libxml2\x86-uwp-dbg\libxml2.vcxproj]
   4>xmlmodule.obj : error LNK2019: unresolved external symbol _LoadLibraryA referenced in function _xmlModulePlatformOpen [E:\vcpkg\buildtrees\libxml2\x86-uwp-dbg\libxml2.vcxproj]
   4>E:\vcpkg\buildtrees\libxml2\x86-uwp-dbg\Debug\libxml2.dll : fatal error LNK1120: 2 unresolved externals [E:\vcpkg\buildtrees\libxml2\x86-uwp-dbg\libxml2.vcxproj]

[ras0219-msft]

Thanks for the PR!

I'm going to go ahead and merge this for now even though we're still waiting on the other PR to add UWP support. If there ends up being some remaining work to do for libxml2 after #5607, we can address that with a follow up :)

[myd7349]

Thanks! :)