[gnome-text-editor] build: use gnu17 std

[Christian Hergert <chergert src gnome org>]

commit 89e0b89e8dbaa7695c8895cf9a4d003509b0ab3f
Author: Christian Hergert <chergert redhat com>
Date:   Wed Feb 2 17:03:34 2022 -0800

    build: use gnu17 std
    
    gnu18 exists when we're on Linux, but the default does not work for when
    we are on macOS as only gnu17 might be available (such as in CI).

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index bbb3c12..b269fa4 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('gnome-text-editor', 'c',
           version: '42.alpha2',
     meson_version: '>= 0.59.1',
-  default_options: [ 'warning_level=2', 'c_std=gnu18' ],
+  default_options: [ 'warning_level=2', 'c_std=gnu17' ],
 )
 
 cc = meson.get_compiler('c')