Make spec backward compatible with F23

qgis.spec

@@ -16,7 +16,14 @@
 # the soname might stay the same, it won't work anymore.
 #http://hub.qgis.org/issues/5274
 
+%if 0%{?fedora} == 23
+%global grass_version 6.4.4
+%endif
+
+%if 0%{?fedora} == 24
 %global grass_version 7.0.3
+%global configure_with_grass7 -D WITH_GRASS7:BOOL=TRUE
+%endif
 
 #TODO: Run test suite (see debian/rules)
 
@@ -216,7 +223,7 @@ export LD_LIBRARY_PATH=%{_builddir}/%{name}-%{version}/output/%{_lib}
       -D WITH_BINDINGS:BOOL=TRUE \
       -D MAPSERVER_SKIP_ECW=TRUE \
       -D WITH_GRASS:BOOL=TRUE \
-      -D WITH_GRASS7:BOOL=TRUE \
+      %{configure_with_grass7} \
       -D GRASS_PREFIX=%{_libdir}/grass \
       -D WITH_MAPSERVER:BOOL=TRUE \
       -D WITH_CUSTOM_WIDGETS:BOOL=TRUE \