Hide all gtest symbols in cudftestutil (#16546)

By hiding the gtest symbols in cudftestutil it allows consumers of the library to build with a differing version of gtest without issue.

Authors:
  - Robert Maynard (https://github.com/robertmaynard)

Approvers:
  - Marcus D. Hanwell (https://github.com/cryos)
  - Bradley Dice (https://github.com/bdice)

URL: #16546

cpp/cmake/thirdparty/get_gtest.cmake

@@ -16,9 +16,18 @@
 function(find_and_configure_gtest)
   include(${rapids-cmake-dir}/cpm/gtest.cmake)
 
+  # Mark all the non explicit googletest symbols as hidden. This ensures that libcudftestutil can be
+  # used by consumers with a different shared gtest.
+  set(gtest_hide_internal_symbols ON)
+
   # Find or install GoogleTest
   rapids_cpm_gtest(BUILD_STATIC)
 
+  # Mark all the explicit googletest symbols as hidden. This ensures that libcudftestutil can be
+  # used by consumers with a different shared gtest.
+  if(TARGET gtest)
+    target_compile_definitions(gtest PUBLIC "$<BUILD_LOCAL_INTERFACE:GTEST_API_=>")
+  endif()
 endfunction()
 
 find_and_configure_gtest()