Building native extensions.  This could take a while...
ERROR:  While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install fxruby
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/usr/bin/ruby
        --with-fox-dir
        --without-fox-dir
        --with-fox-include
        --without-fox-include=${fox-dir}/include
        --with-fox-lib
        --without-fox-lib=${fox-dir}/lib
        --with-fxscintilla-dir
        --without-fxscintilla-dir
        --with-fxscintilla-include
        --without-fxscintilla-include=${fxscintilla-dir}/include
        --with-fxscintilla-lib
        --without-fxscintilla-lib=${fxscintilla-dir}/lib
extconf.rb:31:in `find_installed_fox_version': couldn't find FOX header files (RuntimeError)
        from extconf.rb:157


Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/fxruby-1.6.13 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/fxruby-1.6.13/ext/fox16/gem_make.out