Build libxml2 and libxslt against zlib

This enables the compression support which the lxml unit-tests try to
use.

build.ps1

@@ -24,22 +24,24 @@ $iconvLib = Join-Path (pwd) libiconv_static$x64Dir\Release
 $iconvInc = Join-Path (pwd) ..\source\include
 Set-Location ..\..
 
+Set-Location .\zlib
+Start-Process -NoNewWindow -Wait nmake "-f win32/Makefile.msc zlib.lib"
+$zlibLib = (pwd)
+$zlibInc = (pwd)
+Set-Location ..
+
 Set-Location .\libxml2\win32
-cscript configure.js lib="$iconvLib" include="$iconvInc" vcmanifest=yes
+cscript configure.js lib="$zlibLib;$iconvLib" include="$zlibInc;$iconvInc" vcmanifest=yes zlib=yes
 Start-Process -NoNewWindow -Wait nmake libxmla
 $xmlLib = Join-Path (pwd) bin.msvc
 $xmlInc = Join-Path (pwd) ..\include
 Set-Location ..\..
 
 Set-Location .\libxslt\win32
-cscript configure.js lib="$iconvLib;$xmlLib" include="$iconvInc;$xmlInc" vcmanifest=yes
+cscript configure.js lib="$zlibLib;$iconvLib;$xmlLib" include="$zlibInc;$iconvInc;$xmlInc" vcmanifest=yes zlib=yes
 Start-Process -NoNewWindow -Wait nmake "libxslta libexslta"
 Set-Location ..\..
 
-Set-Location .\zlib
-Start-Process -NoNewWindow -Wait nmake "-f win32/Makefile.msc zlib.lib"
-Set-Location ..
-
 # Pushed by Import-VisualStudioVars
 Pop-EnvironmentBlock