use new %%cmake_build, %%cmake_install macros to fix build

quassel.spec

@@ -100,15 +100,13 @@ Quassel client
 %autosetup -p0 -n %{name}-%{version}
 
 %build
-mkdir build
-pushd build
-%{cmake_kf5} .. -DWANT_MONO=1 -DUSE_QT5=1 -DWITH_KDE=1 -DHAVE_SSL=1
-popd
+%cmake_kf5 \
+  -DWANT_MONO=1 -DUSE_QT5=1 -DWITH_KDE=1 -DHAVE_SSL=1
 
-make %{?_smp_mflags} -C build
+%cmake_build
 
 %install
-make install/fast DESTDIR=%{buildroot} -C build
+%cmake_install
 
 # unpackaged files
 rm -f %{buildroot}/%{_datadir}/pixmaps/quassel.png