FindGTest: Add gtestd_main variant of debug library

Current distributions name the debug library variant as `gtestd_main`
rather than `gtest_maind`.

Fixes: #16940

Modules/FindGTest.cmake

@@ -134,12 +134,12 @@ if(MSVC AND GTEST_MSVC_SEARCH STREQUAL "MD")
     _gtest_find_library(GTEST_LIBRARY            gtest-md  gtest)
     _gtest_find_library(GTEST_LIBRARY_DEBUG      gtest-mdd gtestd)
     _gtest_find_library(GTEST_MAIN_LIBRARY       gtest_main-md  gtest_main)
-    _gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtest_main-mdd gtest_maind)
+    _gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtest_main-mdd gtestd_main gtest_maind)
 else()
     _gtest_find_library(GTEST_LIBRARY            gtest)
     _gtest_find_library(GTEST_LIBRARY_DEBUG      gtestd)
     _gtest_find_library(GTEST_MAIN_LIBRARY       gtest_main)
-    _gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtest_maind)
+    _gtest_find_library(GTEST_MAIN_LIBRARY_DEBUG gtestd_main gtest_maind)
 endif()
 
 include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)