Doc: Added a note about manually selecting the Qt libraries

The Qt 5.1.0 installer by default installs only the desktop
version of the libraries. The user will have to manually
select the libraries for Android x86 and ARMv7, which is
not obvious in the installer.

Change-Id: I77b11cd4ca7069e4ce90fd77d8167ee0c0141320
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>

doc/src/platforms/android.qdoc

@@ -69,6 +69,10 @@ After the SDK is updated, install the Qt 5.1 binaries using the
 to develop for Android. For more information, see
 \l{Qt Creator: Connecting Android Devices}.
 
+\note You must manually choose at least one of the two Qt libraries for Android
+(x86 and ARMv7) from the \gui{Qt 5.1.0} component tree within the \gui{Select
+Components} page of \l{Qt Installation Program}{Qt installation program}.
+
 \section1 Porting an Existing Qt Application
 
 Most Qt applications should be portable to Android with ease, unless they