couchdbx-app build fails on 10.6.8 xcode 4

CompileXIB "Couchbase Server/ToolInstallController.xib"
cd /Users/buildbot/mini64/mac-x64-20-builder/build/build/couchdbx-app
setenv XCODE_DEVELOPER_USR_PATH /Developer/usr/bin/..
/Developer/usr/bin/ibtool --errors --warnings --notices --output-format human-readable-text --compile "/Users/buildbot/mini64/mac-x64-20-builder/build/build/couchdbx-app/build/Release/Couchbase Server.app/Contents/Resources/ToolInstallController.nib" "/Users/buildbot/mini64/mac-x64-20-builder/build/build/couchdbx-app/Couchbase Server/ToolInstallController.xib" --sdk /Developer/SDKs/MacOSX10.6.sdk
/* com.apple.ibtool.errors */
/Users/buildbot/mini64/mac-x64-20-builder/build/build/couchdbx-app/Couchbase Server/ToolInstallController.xib: error: Unable to resolve Interface Builder plug-in dependency for "ToolInstallController.xib". Xcode 4 is missing components necessary to load the following class: IBNSLayoutConstraint. Ensure that Xcode has been properly installed.

• • BUILD FAILED **

The following build commands failed:
CompileXIB "Couchbase Server/ToolInstallController.xib"
(1 failure)
make[1]: *** [couchbase-server-zip] Error 65
make: *** [package-mac] Error 2
program finished with exit code 2
elapsedTime=5125.193439

logs :
http://builds.hq.northscale.net:8010/builders/mac-x64-20-builder/builds/0/steps/couchbase-server%20make%20community%20/logs/stdio