Suppress meson warning

Meson warns that this will be required in the future.  Add it.

Change-Id: I799d868dda86892eea3de4943b238fc3147c9912
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/meson.build b/meson.build
index 732d5a2..2f829da 100644
--- a/meson.build
+++ b/meson.build
@@ -165,7 +165,7 @@
   )
 endif
 
-run_command('cp', '-r', 'specification/json/', meson.current_build_dir())
+run_command('cp', '-r', 'specification/json/', meson.current_build_dir(), check: true)
 run_command('mv', meson.current_build_dir() / 'json', meson.current_build_dir() / 'specification')
 
 if get_option('tests').allowed()