Silence message box occurring after canceling custom executable dialog.

(See also fe2dd584fc5ce998e50aa667044505193256f45f ).

Change-Id: Iffb8f95084955a9ca1cc4b7b0adb558f41811cb4
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Android: Fix in source builds with Qt 5.2

Now the build directory is by default android-build, so by default the
source and build directory don't clash anymore.

Task-number: QTCREATORBUG-10661
Change-Id: I054bd3790f9bc9720536aac301bee192cb9f0429
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>