Fix download of GoogleTest

The instructions for downloading GoogleTest from within CMake
have changed and the old instructions no longer work, breaking
our build.  This commit updates the CMakefile to use the new
instructions and fixes the GoogleTest version we use to 1.11.0.

Signed-off-by: Mark Ryan <[email protected]>

CMakeLists.txt

@@ -9,37 +9,15 @@ OPTION(ENABLE_WERROR "Build with -Werror" OFF)
 
 set (CMAKE_CXX_STANDARD 11)
 
-# Download and unpack googletest at configure time
-configure_file(CMakeLists.txt.in googletest-download/CMakeLists.txt)
-execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
-  RESULT_VARIABLE result
-  WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
-if(result)
-  message(FATAL_ERROR "CMake step for googletest failed: ${result}")
-endif()
-execute_process(COMMAND ${CMAKE_COMMAND} --build .
-  RESULT_VARIABLE result
-  WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
-if(result)
-  message(FATAL_ERROR "Build step for googletest failed: ${result}")
-endif()
-
-# Prevent overriding the parent project's compiler/linker
-# settings on Windows
+include(FetchContent)
+FetchContent_Declare(
+  googletest
+  # GoogleTest 1.11.0
+  URL https://github.com/google/googletest/archive/refs/tags/release-1.11.0.zip
+)
+# For Windows: Prevent overriding the parent project's compiler/linker settings
 set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-
-# Add googletest directly to our build. This defines
-# the gtest and gtest_main targets.
-add_subdirectory(${CMAKE_CURRENT_BINARY_DIR}/googletest-src
-                 ${CMAKE_CURRENT_BINARY_DIR}/googletest-build
-                 EXCLUDE_FROM_ALL)
-
-# The gtest/gtest_main targets carry header search path
-# dependencies automatically when using CMake 2.8.11 or
-# later. Otherwise we have to add them here ourselves.
-if (CMAKE_VERSION VERSION_LESS 2.8.11)
-  include_directories("${gtest_SOURCE_DIR}/include")
-endif()
+FetchContent_MakeAvailable(googletest)
 
 if(NOT CMAKE_BUILD_TYPE)
   set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)