MacPorts 1.9 and portindex generation

[Ryan Schmidt]

Before we release 1.9.0 we should probably resolve this situation, which seems to be a step backward from 1.8.2 behavior:

http://trac.macports.org/ticket/25156

If MacPorts 1.9.0-rc2 is installed on a machine without Xcode installed, the portindex will be missing some ports. (With 1.8.2 a correct full portindex is downloaded; 1.9 attempts to generate it itself and doesn't totally succeed if Xcode isn't there.)