build: switch to C++20

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8e48e5949e210ef9b77ee9c1438f7b7963a12584
diff --git a/meson.build b/meson.build
index 528b1d5..1d14bf1 100644
--- a/meson.build
+++ b/meson.build
@@ -1,10 +1,10 @@
 project('phosphor-time-manager',
         'cpp',
          version: '0.1',
-         meson_version: '>=0.53.2',
+         meson_version: '>=0.57.0',
          default_options: [ 'warning_level=3',
                             'werror=true',
-                            'cpp_std=c++17',
+                            'cpp_std=c++20',
                             'buildtype=debugoptimized' ])
 
 ########################################################################
@@ -21,8 +21,8 @@
 
 # Validate the c++ Standard
 
-if get_option('cpp_std') != 'c++17'
-    error('This project requires cpp std to be in c++17 mode')
+if get_option('cpp_std') != 'c++20'
+    error('This project requires cpp std to be in c++20 mode')
 endif
 
 #########################################################################