More build instructions for Qt5/Fedora

doc/linux.t2t

@@ -204,8 +204,22 @@ sudo debi
 
 == Building QGIS with Qt 5.x ==
 
+/!\ **Warning:** Qt 5 is not officially supported. Building against Qt 5
+libraries seems to work quiet well alrady but be prepared that you are one
+of very few with this setup. We strongly recommend using QGIS with Qt 4.
+
+Python bindings in particular are not expected to be compatible. When Qt 5
+is enabled, the build system automatically activates Python 3 and PyQt5 as well.
+There are no plugins and not even the python code shipped along the QGIS source
+code is compatible with PyQt5.
+
+You have been warned.
+
 == On Fedora Linux ==
 
+We assume that you have the source code of QGIS ready and created a
+new subdirectory called `build` or `build-qt5` in it.
+
 === Install build dependencies ===
 
 ```
@@ -214,9 +228,36 @@ qt5-qtscript-devel qca-qt5-devel python3-qt5-devel python3-qscintilla-qt5-devel
 qscintilla-qt5-devel python3-qscintilla-devel python3-qscintilla-qt5
 clang flex bison geos-devel gdal-devel sqlite-devel libspatialite-devel
 qt5-qtsvg-devel qt5-qtxmlpatterns-devel spatialindex-devel expat-devel proj-devel
-qwt-devel gsl-devel
+qwt-devel gsl-devel postgresql-devel
 ```
 
+Make sure that your build directory is completely empty when you enter the
+following command. Do never try to "re-use" an existing Qt4 build directory.
+If you want to use `ccmake` or other interactive tools, run the following
+command in the empty build directory once before starting to use the interactive
+tools.
+
 ```
 cmake -DENABLE_QT5=ON -DWITH_QWTPOLAR=OFF ..
 ```
+
+If everything went ok you can finally start to compile. (As usual append a -jX
+where X is the number of available cores option to make to speed up your build
+process)
+
+```
+make
+```
+
+Run from the build directory
+
+```
+./output/bin/qgis
+```
+
+Or install to your system
+
+
+```
+make install
+```