meson: Try harder to get c++17

default_options can be overriden, which we don't want.  Fixes build
errors in mesa from trying to build perfetto.cc with c++11.

Change-Id: Ib9d35c81960d4fefb40a3bb091fe002642c8a875

meson.build

diff --git a/meson.build b/meson.build
index 5ef6fce..8fb1e26 100644
--- a/meson.build
+++ b/meson.build
@@ -19,7 +19,6 @@
 project(
     'perfetto',
     ['cpp'],
-    default_options: ['cpp_std=c++17']
 )
 
 fs = import('fs')
@@ -41,6 +40,7 @@
     sources: 'sdk/perfetto.cc',
     dependencies: deps_perfetto,
     install: true,
+    cpp_args: '-std=c++17',
 )
 
 inc_perfetto = include_directories('sdk')