Doc: Qt Versions: Add requirements onto a minimal qt

Some people want to hack, so give them enough rope to start.

Change-Id: Ic8b3f873c322b02c3df91ee267d1e5f07c2ab507
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>

doc/src/projects/creator-projects-qt-versions.qdoc

@@ -75,6 +75,16 @@
 
         \endlist
 
+    \section2 Minimum Requirements
+    If your build of Qt is incomplete but you still want to use QMake as build
+    system, you need to ensure the following minimum requirements to be able to use that setup with \QC.
+    \list 1
+        \li qmake is an executable that understands the -query command line argument.
+        \li The bin and include directories have to exist. \QC fetches these directories by running \c{qmake -query}.
+        \li The mkspecs directory should be complete enough to parse .pro files.
+    \endlist
+
+    If your Qt version has no libQtCore.so, \QC is unable to detect the ABI.
 
 */