build: switch to C++20

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id79f75b9740509bc0c66a251263ac2c443f54acd
diff --git a/meson.build b/meson.build
index e46790b..c204fb3 100644
--- a/meson.build
+++ b/meson.build
@@ -3,9 +3,11 @@
         default_options: [
           'warning_level=3',
           'werror=true',
-          'cpp_std=c++17',
+          'cpp_std=c++20',
           'b_lto=true',
-        ])
+        ],
+        meson_version: '>=0.57.0',
+       )
 
 systemd = dependency('systemd')
 servicedir = systemd.get_pkgconfig_variable('systemdsystemunitdir')