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/test/meson.build b/test/meson.build
index 97e219b..29704ca 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -1,11 +1,11 @@
 gtest = dependency('gtest', main: true, disabler: true, required: false)
 gmock = dependency('gmock', disabler: true, required: false)
 if not gtest.found() or not gmock.found()
+  gtest_opts = import('cmake').subproject_options()
+  gtest_opts.add_cmake_defines({'CMAKE_CXX_FLAGS': '-Wno-pedantic'})
   gtest_proj = import('cmake').subproject(
     'googletest',
-    cmake_options: [
-      '-DCMAKE_CXX_FLAGS=-Wno-pedantic',
-    ],
+    options: gtest_opts,
     required: false)
   if gtest_proj.found()
     gtest = declare_dependency(