libv8 and rubyracer error after using gem install libv8 -v '3.16.14.3' -- --with-system-v8

Installing therubyracer 0.12.1 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

C:/Ruby21/bin/ruby.exe extconf.rb

checking for main() in -lpthread... no checking for v8.h... no * 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=C:/Ruby21/bin/ruby --with-pthreadlib --without-pthreadlib --enable-debug --disable-debug --with-v8-dir --without-v8-dir --with-v8-include --without-v8-include=${v8-dir}/include --with-v8-lib --without-v8-lib=${v8-dir}/lib C:/Ruby21/lib/ruby/gems/2.1.0/gems/libv8-3.16.14.3/ext/libv8/location.rb:50:in ` configure': You have chosen to use the version of V8 found on your system (Libv8 ::Location::System::NotFoundError) and not the one that is bundle with the libv8 rubygem. However, it could not be located. please make sure you have a version of v8 that is compatible with 3.16.14.3 installed. You may need to special --with-v8-dir options if it is in a non-standard location

thanks, The Mgmt

    from C:/Ruby21/lib/ruby/gems/2.1.0/gems/libv8-3.16.14.3/lib/libv8.rb:7:i

n configure_makefile' from extconf.rb:32:in'

extconf failed, exit code 1

Gem files will remain installed in C:/Ruby21/lib/ruby/gems/2.1.0/gems/therubyrac er-0.12.1 for inspection. Results logged to C:/Ruby21/lib/ruby/gems/2.1.0/extensions/x86-mingw32/2.1.0/the rubyracer-0.12.1/gem_make.out An error occurred while installing therubyracer (0.12.1), and Bundler cannot continue. Make sure that gem install therubyracer -v '0.12.1' succeeds before bundling.