waffle's upstream intentionally does not ship cmake files anymore
(just a quick fix that works for us, there may be more to consider)

https://bugs.gentoo.org/901365
https://gitlab.freedesktop.org/mesa/waffle/-/issues/74
https://gitlab.freedesktop.org/mesa/waffle/-/commit/a16983fea590491727c8119256c7b938fe1f9d10
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -195,3 +195,4 @@
     # Use Waffle for eglretrace
-    find_package (Waffle REQUIRED)
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(Waffle REQUIRED waffle-1)
 endif ()