updated build system

cmake/libraries/testing.cmake

@@ -0,0 +1,18 @@
+if(NOT PROJECT_BUILD AND PROJECT_ENABLE_TESTING)
+  if(NOT PROJECT_IS_MINGW OR CMAKE_HOST_WIN32)
+    ExternalProject_Add(gtest_project
+      PREFIX external
+      URL ${PROJECT_3RD_PARTY_DIR}/googletest-${GTEST_VERSION}.tar.gz
+      URL_HASH SHA256=7315acb6bf10e99f332c8a43f00d5fbb1ee6ca48c52f6b936991b216c586aaad
+      LIST_SEPARATOR |
+      CMAKE_ARGS ${PROJECT_EXTERNAL_CMAKE_FLAGS}
+        -DBUILD_SHARED_LIBS=${PROJECT_BUILD_SHARED_LIBS}
+        -DBUILD_STATIC_LIBS=ON
+    )
+
+    set(PROJECT_DEPENDENCIES 
+      ${PROJECT_DEPENDENCIES}
+      gtest_project
+    )
+  endif()
+endif()