Error Installing Compass

$ sudo gem install compass
Password:
Building native extensions.  This could take a while...
ERROR:  Error installing compass:
    ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20140929-12546-aemop2.rb extconf.rb
*** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
    --with-ffi_c-dir
    --without-ffi_c-dir
    --with-ffi_c-include
    --without-ffi_c-include=${ffi_c-dir}/include
    --with-ffi_c-lib
    --without-ffi_c-lib=${ffi_c-dir}/
    --with-libffi-config
    --without-libffi-config
    --with-pkg-config
    --without-pkg-config
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:1501:in `split': invalid byte sequence in UTF-8 (ArgumentError)
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:1501:in `find_executable0'
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:1716:in `pkg_config'
    from extconf.rb:15:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/ffi-1.9.5 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/ffi-1.9.5/gem_make.out
duartes-imac:~ monteiro$