build: Require C++20 compiler

depends/packages/qt.mk

@@ -41,7 +41,7 @@ $(package)_config_opts_release += -silent
 $(package)_config_opts_debug = -debug
 $(package)_config_opts_debug += -optimized-tools
 $(package)_config_opts += -bindir $(build_prefix)/bin
-$(package)_config_opts += -c++std c++17
+$(package)_config_opts += -c++std c++2a
 $(package)_config_opts += -confirm-license
 $(package)_config_opts += -hostprefix $(build_prefix)
 $(package)_config_opts += -no-compile-examples