Make code compile on clang

We use c++26 featuresin stdexec (something in unpack fold expressions)
that clang warns about because this is only enabled for c++23.

Ignore the warning for now.  Can be removed when we're on c++26

Change-Id: I10b7c216c63d97b865741025873d32666e6a7440
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/meson.build b/meson.build
index bc5a837..173bff6 100644
--- a/meson.build
+++ b/meson.build
@@ -13,6 +13,10 @@
     version: '1.0.0',
     meson_version: '>=1.1.1',
 )
+cxx = meson.get_compiler('cpp')
+if (cxx.get_id() == 'clang')
+    add_project_arguments(['-Wno-c++26-extensions'], language: 'cpp')
+endif
 
 libsystemd_pkg = dependency('libsystemd')
 nlohmann_json_dep = dependency('nlohmann_json', include_type: 'system')