Rails Mysql Installation on MacOS - CMake Error -

i've got issue installation of mysql ruby on rails on macos snow leopard. follow tutorial on website http://michaelfarmer.info/preferred-rails-3-and-mysql-installation-on-o.
@ step of mysql installation (brew install mysql), terminal exposes error is:

cmake error: parse error in cache file /tmp/homebrew-cmake-2.8.4-fyto/cmake-2.8.4/cmakecache.txt. offending entry: /sdks/macosx10.6.sdk

i found out problem comes fact xcode not installed in default directory "/developer". explained here : https://github.com/mxcl/homebrew/issues/5182

at point, i'm lost, supposed ?

here's brew --config

homebrew_version: 0.8
head: (none)
homebrew_prefix: /usr/local
homebrew_cellar: /usr/local/cellar
homebrew_repository: /usr/local
homebrew_library_path: /usr/local/library/homebrew
hardware: dual-core 64-bit core2
os x: 10.6.7
kernel architecture: i386
ruby: 1.8.7-174
/usr/bin/ruby => /system/library/frameworks/ruby.framework/versions/1.8/usr/bin/ruby
xcode: 3.2.5
gcc-4.0: build 5494
gcc-4.2: build 5664
llvm: build 2333
macports or fink? false
x11 installed? true

thanks in advance help. camille.

if you're able to, make symbolic link path have xcode installed @ /developer:

ln -s /path/to/xcode /developer 

and cmake (and mysql) compile. (i keep xcode on secondary drive since primary tiny ssd, , worked me).