Ruby 1.9.3-p0, Rails 3.1.3, bundle install で発生

error

$ gem install mysql2 -v '0.3.11'                                                                              git:master*
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
	ERROR: Failed to build gem native extension.

        /Users/koichi/.rvm/rubies/ruby-1.9.3-p0/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... yes
checking for rb_wait_for_single_fd()... yes
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
creating Makefile

make
compiling client.c
client.c: In function 'rb_raise_mysql2_error':
client.c:98: warning: ISO C90 forbids mixed declarations and code
client.c: In function 'rb_mysql_client_socket':
client.c:590: warning: ISO C90 forbids mixed declarations and code
client.c: In function 'set_connect_timeout':
client.c:673: warning: passing argument 3 of 'mysql_options' from incompatible pointer type
compiling mysql2_ext.c
compiling result.c
linking shared-object mysql2/mysql2.bundle
ld: library not found for -lmysqlclient_r
collect2: ld returned 1 exit status
make: *** [mysql2.bundle] Error 1