Build nokogiri 1.6.8 at Mac OS X 10.11

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    /Users/hchu/.rvm/rubies/ruby-2.0.0-p247/bin/ruby extconf.rb

Using pkg-config version 1.1.7
checking if the C compiler accepts ... yes
checking if the C compiler accepts -Wno-error=unused-command-line-argument-hard-error-in-future... no
Building nokogiri using packaged libraries.
Using mini_portile version 2.1.0
checking for iconv.h... yes
checking for gzdopen() in -lz... yes
checking for iconv... yes

************************************************************************

IMPORTANT NOTICE:

Building Nokogiri with a packaged version of libxml2-2.9.4.

Team Nokogiri will keep on doing their best to provide security

updates in a timely manner, but if this is a concern for you and want

to use the system library instead; abort this installation process and

reinstall nokogiri as follows:

    gem install nokogiri -- --use-system-libraries
        [--with-xml2-config=/path/to/xml2-config]
        [--with-xslt-config=/path/to/xslt-config]


If you are using Bundler, tell it to use the option:

    bundle config build.nokogiri --use-system-libraries
    bundle install

Note, however, that nokogiri is not fully compatible with arbitrary

versions of libxml2 provided by OS/package vendors.

************************************************************************

Extracting libxml2-2.9.4.tar.gz into tmp/x86_64-apple-darwin12.3.0/ports/libxml2/2.9.4... OK
Running 'configure' for libxml2 2.9.4... OK
Running 'compile' for libxml2 2.9.4... ERROR, review '/Users/hchu/.rvm/gems/ruby-2.0.0-p247/gems/nokogiri-1.6.8/ext/nokogiri/tmp/x86_64-apple-darwin12.3.0/ports/libxml2/2.9.4/compile.log' to see what happened. Last lines are:

========================================================================

    unsigned short* in = (unsigned short*) inb;

                         ^~~~~~~~~~~~~~~~~~~~~
encoding.c:815:27: warning: cast from 'unsigned char *' to 'unsigned short *' increases required alignment from 1 to 2 [-Wcast-align]

    unsigned short* out = (unsigned short*) outb;

                          ^~~~~~~~~~~~~~~~~~~~~~
4 warnings generated.
  CC       error.lo
  CC       parserInternals.lo
  CC       parser.lo
  CC       tree.lo
  CC       hash.lo
  CC       list.lo
  CC       xmlIO.lo
xmlIO.c:1450:52: error: use of undeclared identifier 'LZMA_OK'

    ret =  (__libxml2_xzclose((xzFile) context) == LZMA_OK ) ? 0 : -1;
                                                   ^

1 error generated.

make[2]: *** [xmlIO.lo] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2