New meson is more picky about using exe in test() that wasn't found.
https://bugs.gentoo.org/843866
--- a/data/meson.build
+++ b/data/meson.build
@@ -41,9 +41,11 @@
 )
 
-test(
-    'validate-appstream',
-    appstream_util,
-    args: ['--nonet', 'validate-relax', gmult_appdata],
-)
+if appstream_util.found()
+    test(
+        'validate-appstream',
+        appstream_util,
+        args: ['--nonet', 'validate-relax', gmult_appdata],
+    )
+endif
 
 resources = gnome.compile_resources(