explicitly specify warnlevel in meson

we can't turn on 2 (or 3...) yet, since the warnings are too many

meson.build

@@ -1,6 +1,8 @@
 project('octacore', ['cpp'],
     version: '0.0.1',
-    default_options: ['buildtype=debugoptimized', 'cpp_std=c++17'],
+    default_options: [
+        'buildtype=debugoptimized', 'cpp_std=c++17', 'warning_level=1'
+    ],
     meson_version: '>=0.46'
 )