nu2: fatal error: 'Foundation/Foundation.h' file not found

[ryandesign@…]

nu2 ​fails to build on the lion buildbot:

--->  Configuring nu2
DEBUG: Using compiler 'Mac OS X clang'
DEBUG: Executing org.macports.configure (nu2)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: build phase started at Fri May 11 00:59:33 PDT 2012
--->  Building nu2
DEBUG: Executing proc-pre-org.macports.build-build-0
/usr/bin/clang -g -Wall -DMININUSH  -DMACOSX -DDARWIN    -fobjc-exceptions -I/opt/local/lib/libffi-3.0.10/include   -I./include -I/opt/local/include -c objc/Nu.m -o objc/Nu.o
/usr/bin/clang -g -Wall -DMININUSH  -DMACOSX -DDARWIN    -fobjc-exceptions -I/opt/local/lib/libffi-3.0.10/include   -I./include -I/opt/local/include -c main/main.m -o main/main.o
/usr/bin/clang  objc/Nu.o  main/main.o  -g -Wall -DMININUSH  -DMACOSX -DDARWIN    -o mininush -framework Cocoa -lobjc -lreadline -L/opt/local/lib -L/opt/local/lib -lffi  
DEBUG: Executing org.macports.build (nu2)
DEBUG: Environment: CPATH='/opt/local/include' CC_PRINT_OPTIONS_FILE='/opt/local/var/macports/build/_Volumes_work_mports_dports_devel_nu2/nu2/work/.CC_PRINT_OPTIONS' LIBRARY_PATH='/opt/local/lib' CC_PRINT_OPTIONS='YES' MACOSX_DEPLOYMENT_TARGET='10.7' PREFIX='/opt/local' GI_SCANNER_DISABLE_CACHE='1'
DEBUG: Assembled command: 'cd "/opt/local/var/macports/build/_Volumes_work_mports_dports_devel_nu2/nu2/work/Nu-2.0.1" && ./mininush tools/nuke'
DEBUG: Executing command line:  cd "/opt/local/var/macports/build/_Volumes_work_mports_dports_devel_nu2/nu2/work/Nu-2.0.1" && ./mininush tools/nuke 
objc/Nu.m:29:9: fatal error: 'Foundation/Foundation.h' file not found
#import <Foundation/Foundation.h>
        ^
1 error generated.