Is it possible to customize the default order of Spotlight's results?
I face the same problem. I overcame it by excluding Xcode Server Builder.app from Spotlight search results.

Locate Xcode Server Builder.app by navigating to /Applications/Xcode.app/Contents/Developer/Applications directory. Now, go to System Preferences → Spotlight → Privacy tab. Drag and drop Xcode Server Builder.app from the Finder window into the list under Privacy tab.



Now, the Xcode Server Builder.app will no longer appear in the Spotlight search results. This should take care of accidentally launching it instead of Xcode.app.

In case you still need to launch Xcode Server Builder.app on an infrequent basis, you can either drag and drop the app into Dock to create a shortcut, or press and hold Command + Option and drag the app icon to any convenient location to create a shortcut link to the app.