Description: Use c++20 to build GUI
Fixes "src/include/open-axiom/vm:177:21: error: ‘std::same_as’ has not been declared"

Index: open-axiom-debian/src/gui/gui.pro.in
===================================================================
--- open-axiom-debian.orig/src/gui/gui.pro.in
+++ open-axiom-debian/src/gui/gui.pro.in
@@ -60,5 +60,5 @@ LIBS += $$OA_LIB
 
 ## C++ compiler
 QMAKE_CXX = @CXX@
-QMAKE_CXXFLAGS += -std=c++11 @oa_extra_cxxflags@
+QMAKE_CXXFLAGS += -std=c++20 @oa_extra_cxxflags@
 QMAKE_LINK = @CXX@