workaround for mysql 5.6.12's mysql_config

mysql_config from mysql 5.6.12 includes various -W flags that are not supposed by OS X's gcc. this just trims them out. hopefully it gets fixed upstream though.

thanks to @zimbatm - see Homebrew#20788

Author: vito

Library/Formula/mysql.rb

@@ -98,6 +98,7 @@ def install
 
     system "cmake", *args
     system "make"
+    inreplace "scripts/mysql_config", / -W[\w-]+ /, " "
     system "make install"
 
     # Don't create databases inside of the prefix!