Only download GTest in Superbuild

Do not build GTest in the Superbuild allow GTest to be built as a
subdirectory of the SimpleITK main project.

Change-Id: I2f984b255a185e1b0404b4c142b839bccac3a34f

SuperBuild/External_GTest.cmake

@@ -11,56 +11,20 @@ set(GTEST_TARGET_VERSION 1.8.0)
 set(GTEST_DOWNLOAD_SOURCE_HASH "16877098823401d1bf2ed7891d7dce36")
 
 # follow the standard EP_PREFIX locations
-set(GTEST_binary_dir ${CMAKE_CURRENT_BINARY_DIR}/${proj}-prefix/src/${proj}-build)
 set(GTEST_source_dir ${CMAKE_CURRENT_BINARY_DIR}/${proj}-prefix/src/${proj})
-set(GTEST_install_dir ${CMAKE_CURRENT_BINARY_DIR}/${proj})
 
 sitkSourceDownload(GTEST_URL "googletest-release-${GTEST_TARGET_VERSION}.tar.gz" ${GTEST_DOWNLOAD_SOURCE_HASH})
 
-file(WRITE "${GTEST_binary_dir}/CMakeCacheInit.txt" "${ep_common_cache}" )
-
-set(${proj}_ARCHIVE_OUTPUT_DIRECTORY "<BINARY_DIR>/lib")
-if (CMAKE_GENERATOR MATCHES "Visual Studio")
-  set(${proj}_ARCHIVE_OUTPUT_DIRECTORY "<BINARY_DIR>/lib/$<CONFIG>")
-endif()
-
-set(ep_extra_args)
-if(MSVC_VERSION EQUAL 1700)
-  # Tuples are limited by _VARIADIC_MAX in VS11. The variadic
-  # templates are not deep enough by default. We are not currently
-  # using the GTest features which require tuple, so just disable them
-  # and hope that upstream premanetly addresses the problem, with out
-  # required more CMake core for compiler issues.
-  set(ep_extra_args ${ep_extra_args} -D CMAKE_CXX_FLAGS=-DGTEST_HAS_TR1_TUPLE=0 ${CMAKE_CXX_FLAGS})
-endif()
-
-if(MSVC)
-  set(ep_extra_args ${ep_extra_args} -D gtest_force_shared_crt:BOOL=ON)
-endif()
-
-
 ExternalProject_Add(${proj}
   URL "${GTEST_URL}"
   URL_MD5 ${GTEST_DOWNLOAD_SOURCE_HASH}
-  INSTALL_DIR ${GTEST_install_dir}
-  CMAKE_GENERATOR ${gen}
-  CMAKE_ARGS
-    --no-warn-unused-cli
-    -C "${GTEST_binary_dir}/CMakeCacheInit.txt"
-    ${ep_common_args}
-    ${ep_extra_args}
-    -DBUILD_GMOCK:BOOL=OFF
-    -DBUILD_GTEST:BOOL=ON
-    -DBUILD_SHARED_LIBS:BOOL=OFF
-    -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY:PATH=<BINARY_DIR>/lib
-    -Dgtest_disable_pthreads:BOOL=ON
-  INSTALL_COMMAND
-      ${CMAKE_COMMAND} -E copy_directory ${${proj}_ARCHIVE_OUTPUT_DIRECTORY} <INSTALL_DIR>/lib
-    COMMAND
-      ${CMAKE_COMMAND} -E copy_directory <SOURCE_DIR>/googletest/include <INSTALL_DIR>/include
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
   ${External_Project_USES_TERMINAL}
 )
 
 sitkSourceDownloadDependency(${proj})
 
-set(GTEST_ROOT ${GTEST_install_dir})
+set(GTEST_ROOT ${GTEST_source_dir}/googletest)

SuperBuild/SuperBuild.cmake

@@ -326,10 +326,13 @@ mark_as_advanced(USE_SYSTEM_GTEST)
 if ( BUILD_TESTING )
   if (USE_SYSTEM_GTEST)
     find_package( GTest REQUIRED )
-    list(APPEND SimpleITK_VARS GTEST_LIBRARIES GTEST_INCLUDE_DIRS GTEST_MAIN_LIBRARIES)
+    if (GTEST_FOUND AND TARGET "${GTEST_LIBRARIES}" AND DEFINED GTEST_ROOT)
+      list(APPEND SimpleITK_VARS GTEST_ROOT)
+    else()
+      list(APPEND SimpleITK_VARS GTEST_LIBRARIES GTEST_INCLUDE_DIRS GTEST_MAIN_LIBRARIES)
+    endif()
   else()
     include(External_GTest)
-    set( GTEST_ROOT ${GTEST_ROOT} )
     list(APPEND SimpleITK_VARS GTEST_ROOT)
     list(APPEND ${CMAKE_PROJECT_NAME}_DEPENDENCIES GTest)
   endif()