build: switch to c++20

Change-Id: Ibe16889749f6b61a3bc8d9a2979b0f7a789cbc24
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meson.build b/meson.build
index 3c536af..ef744e6 100644
--- a/meson.build
+++ b/meson.build
@@ -2,11 +2,12 @@
     'phosphor-objmgr',
     'c', 'cpp',
     default_options: [
-        'cpp_std=c++17',
+        'cpp_std=c++20',
         'warning_level=3',
         'werror=true',
     ],
     license: 'Apache-2.0',
+    meson_version: '>=0.57.0',
     version: '1.0',
 )