C:\devkit>gem install mysql2 -- '--with-mysql-lib="C:\xampp\mysql\lib\opt" --wit
h-mysql-include="C:\xampp\mysql\include"
Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
The system cannot find the path specified.
ERROR:  Error installing mysql2:
        ERROR: Failed to build gem native extension.

        C:/Ruby192/bin/ruby.exe extconf.rb --with-mysql-lib="C:\xampp\mysql\lib\
opt" --with-mysql-include="C:\xampp\mysql\include"
checking for rb_thread_blocking_region()... yes
checking for main() in -llibmysql... yes
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
creating Makefile


Gem files will remain installed in C:/Ruby192/lib/ruby/gems/1.9.1/gems/mysql2-0.
3.7 for inspection.
Results logged to C:/Ruby192/lib/ruby/gems/1.9.1/gems/mysql2-0.3.7/ext/mysql2/ge
m_make.out