QMAKE_CLEAN items with wildcards in symbian-abld builds will halt the build without obvious reason.

If there is a wildcard in QMAKE_CLEAN item, symbian-abld build will halt without showing why. This happens because abld build is not printing the (Y/N) question to confirm wildcard delete but still waits user to answer it. Apparently some projects are using QMAKE_CLEAN with wildcards (see internal https://qtrequirements.europe.nokia.com/browse/QTPROD-875 for fixing the issue for symbian-sbsv2), so this is pretty bad.

This problem was introduced by fix for QTBUG-16893 (included in 4.7.4), which added QMAKE_CLEAN handling to symbian-abld as means to clean .mif files; previously QMAKE_CLEAN was just ignored in symbian-abld. Therefore this fix should also be included into 4.7.4 to avoid regressions.

Note that QMAKE_DISTCLEAN for both symbian-sbsv2 and symbian-abld also asks the (Y/N) question, but there the question shows up on screen, at least when building on command line. Fixing QMAKE_CLEAN will most likely fix this as a freebie, too.