formula: trap CMake FetchContent usage instead of using FETCHCONTENT_FULLY_DISCONNECTED

Library/Homebrew/cmake/trap_fetchcontent_provider.cmake

@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 3.24) # Dependency providers introduced in CMake 3.24
+
+option(HOMEBREW_ALLOW_FETCHCONTENT "Allow FetchContent to be used in Homebrew builds" OFF)
+
+if (HOMEBREW_ALLOW_FETCHCONTENT)
+    return()
+endif()
+
+macro(trap_fetchcontent_provider method depName)
+    message(FATAL_ERROR "Refusing to populate dependency '${depName}' with FetchContent while building in Homebrew, please use a formula dependency or add a resource to the formula.")
+endmacro()
+
+cmake_language(
+    SET_DEPENDENCY_PROVIDER trap_fetchcontent_provider
+    SUPPORTED_METHODS FETCHCONTENT_MAKEAVAILABLE_SERIAL
+)

Library/Homebrew/formula.rb

@@ -1808,7 +1808,7 @@ class Formula
       -DCMAKE_BUILD_TYPE=Release
       -DCMAKE_FIND_FRAMEWORK=#{find_framework}
       -DCMAKE_VERBOSE_MAKEFILE=ON
-      -DFETCHCONTENT_FULLY_DISCONNECTED=ON
+      -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES=#{HOMEBREW_LIBRARY_PATH}/cmake/trap_fetchcontent_provider.cmake
       -Wno-dev
       -DBUILD_TESTING=OFF
     ]