Improve compatibility with new CMake macro

Signed-off-by: Igor Raits <ignatenkobrain@fedoraproject.org>

xournalpp.spec

@@ -1,3 +1,4 @@
+%global __cmake_in_source_build 1
 %global         _with_cppunit 1
 
 Name:           xournalpp
@@ -57,15 +58,16 @@ sed -i 's|tlh-AA|tlh|g' po/tlh.po
 
 %build
 %cmake3 \
-        %{_with_cppunit: -DENABLE_CPPUNIT=ON} \
+        %{?_with_cppunit: -DENABLE_CPPUNIT=ON} \
-        .
+	%{nil}
 
+%cmake3_build
 # Add translations parameter
 # https://github.com/xournalpp/xournalpp/issues/1596
-%make_build translations
+%cmake3_build --target translations
 
 %install
-%make_install
+%cmake3_install
 
 #Remove depreciated key from desktop file
 #Fix desktop file associated with application