If running on Windows, then add the current directory to the PATH for the
current process so it can find the pre-built libxml2 and iconv2 shared
libraries (dlls).
Required files
libxml_ruby
libxml/error
libxml/parser
libxml/document
libxml/namespaces
libxml/namespace
libxml/node
libxml/ns
libxml/attributes
libxml/attr
libxml/attr_decl
libxml/tree
libxml/reader
libxml/html_parser
libxml/sax_parser
libxml/sax_callbacks
libxml/xpath_object
libxml/properties