build: fix warning about using -Wextra flag

Each build, meson would issue a warning reporting that the
"warning_level" setting should be used in place of adding -Wextra
directly to our build commands. Testing with meson 0.61 shows that the
only difference for gcc and clang builds between warning levels 1 and
2 is the addition of -Wextra, so we can remove the warning by deleting
our explicit set of Wextra and changing the build defaults to
warning_level 2.

Fixes: 524a0d5d66 ("build: enable extra warnings with meson")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Luca Boccassi <bluca@debian.org>

config/meson.build

@@ -247,10 +247,9 @@ endif
 add_project_arguments('-include', 'rte_config.h', language: 'c')
 
 # enable extra warnings and disable any unwanted warnings
+# -Wall is added by default at warning level 1, and -Wextra
+# at warning level 2 (DPDK default)
 warning_flags = [
-        # -Wall is added by meson by default, so add -Wextra only
-        '-Wextra',
-
         # additional warnings in alphabetical order
         '-Wcast-qual',
         '-Wdeprecated',

meson.build

@@ -7,7 +7,11 @@ project('DPDK', 'C',
         version: run_command(find_program('cat', 'more'),
             files('VERSION'), check: true).stdout().strip(),
         license: 'BSD',
-        default_options: ['buildtype=release', 'default_library=static'],
+        default_options: [
+            'buildtype=release',
+            'default_library=static',
+            'warning_level=2',
+        ],
         meson_version: '>= 0.49.2'
 )