meson: Update minimum version to 0.57.0

Required for c++20 suppport.

Change-Id: I3d34c7ebecbb9b7a1f1f8fe43f7b36f8d1581979
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/meson.build b/src/meson.build
index 288186b..29877dd 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -7,11 +7,11 @@
   dependencies: function2_dep,
   required: false)
 if not has_function2
+  function2_opts = import('cmake').subproject_options()
+  function2_opts.add_cmake_defines({'BUILD_TESTING': 'OFF'})
   function2_proj = import('cmake').subproject(
     'function2',
-    cmake_options: [
-      '-DBUILD_TESTING=OFF',
-    ],
+    options: function2_opts,
     required: false)
   assert(function2_proj.found(), 'function2 is required')
   if function2_proj.found()