FetchContent: Fix protobuf example to avoid CMP0077 warning

The protobuf example would raise a "Policy CMP0077" warning and
protobuf tests would still be built, e.g. setting the variable is
ignored in latest CMake. Set an INTERNAL cache variable instead so
that CMP0077 warnings won't be triggered.

1 files changed, 4 insertions, 3 deletions

diff --git a/Modules/FetchContent.cmake b/Modules/FetchContent.cmake
index d016fb5aed..9747cd9559 100644
--- a/Modules/FetchContent.cmake
+++ b/Modules/FetchContent.cmake
@@ -881,9 +881,10 @@ Overriding Where To Find CMakeLists.txt
 
 If the sub-project's ``CMakeLists.txt`` file is not at the top level of its
 source tree, the ``SOURCE_SUBDIR`` option can be used to tell ``FetchContent``
-where to find it.  The following example shows how to use that option and
+where to find it.  The following example shows how to use that option, and
 it also sets a variable which is meaningful to the subproject before pulling
-it into the main build:
+it into the main build (set as an ``INTERNAL`` cache variable to avoid
+problems with policy :policy:`CMP0077`):
 
 .. code-block:: cmake
 
@@ -894,7 +895,7 @@ it into the main build:
     GIT_TAG        ae50d9b9902526efd6c7a1907d09739f959c6297 # v3.15.0
     SOURCE_SUBDIR  cmake
   )
-  set(protobuf_BUILD_TESTS OFF)
+  set(protobuf_BUILD_TESTS OFF CACHE INTERNAL "")
   FetchContent_MakeAvailable(protobuf)
 
 Complex Dependency Hierarchies