Unable to get MacPort functionality after installing Xcode 4.3
Everything will start working fine after installation of "Command Line Tools for Xcode" package.You can get it from here: https://developer.apple.com/downloads/index.action#
Please see the MacPorts migration instructions for Xcode 4.3.
The instructions are pretty involved. You need to run xcode-select to set a new tools path, update developer_dir in macports.conf (as described by Henk Poley), re-install MacPorts (ouch), and finally uninstall and re-install all of your ports (double ouch).
Edit: libpvx still wouldn't install after the above. Two extra steps were required:
sudo ln -s /Developer /sudo ln -s /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs /SDKs
YMMV if you have different ports installed!