When creating a completely new Qt Quick application or Qt Quick Controls application with the project creation wizard, including an otherwise working ios kit, in a location that contains a space in the pathname (i.e. /Users/<username>/Documents/Project Code/<projectname>), qmake will fail and the run option will be greyed out.
Hitting "build" the first time will result in "Failed to parse qmlimportscanner output" and "[iphoneos-debug] Error 66", subsequent times result only in the 66. The same is true for [iphonesimulator-debug].
At the same time, compiling the exact same project for macOS or Android works fine. Also, putting the same project into a location without space in the path works fine and builds/runs for iOS.
This suggests the bug is not very recent, but of course might be unrelated: http://stackoverflow.com/questions/26922104/error-failed-to-parse-qmlimportscanner-output/34638304#34638304