This is an upstream macports error that is being fixed; I'm opening an issue here so I don't forget what the problem and resolution are.
The underlying bug and fix: https://trac.macports.org/changeset/96896
Description of the problem:
Using the latest macports qt4-mac (qt4-mac-4.8.2_1+framework+quartz.darwin_10.i386.tbz2 from http://macports.packages.ionic.de/qt4-mac), qmake run as: qmake RELEASE=1 USE_UPNP=1 USE_QRCODE=1 -o Makefile bitcoin-qt.pro
I get a link error:
/usr/bin/g++-4.2 ..... -F/opt/local/Library/Frameworks -F/opt/local/lib -lQtGui -lQtCore ld: library not found for -lQtGui
WORKAROUND:
Explicitly set QMAKE_FRAMEWORKDIR_QT:
qmake QMAKE_FRAMEWORKDIR_QT=/opt/local/Library/Frameworks RELEASE=1 USE_UPNP=1 USE_QRCODE=1 -o Makefile bitcoin-qt.pro