(PA-5715) Download release tarballs for libxml2 and libxslt

Previously, we were using internally hosted libxml2 and libxslt tarballs to
work around the fact that upstream source tarballs don't contain a configure
script.

There are two different issues preventing us from generating the configure
script:

1. libxml2's configure.ac added a requirement on automake 1.16 to resolve an
   issue when building using python, but not all of our systems have 1.16 available:

    AM_INIT_AUTOMAKE([1.16.3 foreign no-dist-gzip dist-xz])

2. We explicitly disable python, so the automake 1.16.3 requirement isn't
   actually needed:

    ./configure --prefix=/opt/puppetlabs/puppet --without-python ...

In theory we could patch configure.ac and run `autoreconf -fi`, but we don't
have new enough libtool installed on all of our systems.

So just install the release tarballs that do contain a configure script.

Author: joshcooper

configs/components/libxml2.rb

@@ -1,12 +1,10 @@
 component "libxml2" do |pkg, settings, platform|
   pkg.version '2.10.3'
-  pkg.sha256sum '26d2415e1c23e0aad8ca52358523fc9116a2eb6e4d4ef47577b1635c7cee3d5f'
-  pkg.url "#{settings[:buildsources_url]}/libxml2-#{pkg.get_version}.tar.gz"
+  pkg.sha256sum '5d2cc3d78bec3dbe212a9d7fa629ada25a7da928af432c93060ff5c17ee28a9c'
 
-  # Newer versions of libxml2 either ship as tar.xz or do not ship with a configure file
-  # and require a newer version of GNU Autotools to generate. This causes problems with
-  # the older and esoteric (AIX, Solaris) platforms that we support.
-  # So we generate a configure file manually, compress as tar.gz, and host internally.
+  libxml2_version_y = pkg.get_version.gsub(/(\d+)\.(\d+)\.(\d+)/, '\1.\2')
+  pkg.url "https://download.gnome.org/sources/libxml2/#{libxml2_version_y}/libxml2-#{pkg.get_version}.tar.xz"
+  pkg.mirror "#{settings[:buildsources_url]}/libxml2-#{pkg.get_version}.tar.xz"
 
   if platform.is_aix?
     if platform.name == 'aix-7.1-ppc'

configs/components/libxslt.rb

@@ -1,12 +1,10 @@
 component "libxslt" do |pkg, settings, platform|
   pkg.version '1.1.37'
-  pkg.sha256sum 'a4ecab265f44e888ed3b39e11c7e925103ef6e26e09d62e9381f26977df96343'
-  pkg.url "#{settings[:buildsources_url]}/libxslt-v#{pkg.get_version}.tar.gz"
+  pkg.sha256sum '3a4b27dc8027ccd6146725950336f1ec520928f320f144eb5fa7990ae6123ab4'
 
-  # Newer versions of libxslt either ship as tar.xz or do not ship with a configure file
-  # and require a newer version of GNU Autotools to generate. This causes problems with
-  # the older and esoteric (AIX, Solaris) platforms that we support.
-  # So we generate a configure file manually, compress as tar.gz, and host internally.
+  libxslt_version_y = pkg.get_version.gsub(/(\d+)\.(\d+)\.(\d+)/, '\1.\2')
+  pkg.url "https://download.gnome.org/sources/libxslt/#{libxslt_version_y}/libxslt-#{pkg.get_version}.tar.xz"
+  pkg.mirror "#{settings[:buildsources_url]}/libxslt-#{pkg.get_version}.tar.xz"
 
   pkg.build_requires "libxml2"