Updated cmake to better organize folders and options.

This adds solution folders that properly group gtest/glslang/hlsl.
This also marks gtest options as advanced so they don't show up
in cmake-gui by default.

External/CMakeLists.txt

@@ -10,6 +10,24 @@ elseif(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/googletest)
     set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
   endif(WIN32)
   add_subdirectory(googletest)
+  set(GTEST_TARGETS
+    gtest
+    gtest_main
+    gmock
+    gmock_main
+  )
+  foreach(target ${GTEST_TARGETS})
+    set_property(TARGET ${target} PROPERTY FOLDER gtest)
+  endforeach()
+  mark_as_advanced(gmock_build_tests
+    BUILD_GMOCK
+    BUILD_GTEST
+    BUILD_SHARED_LIBS
+    gtest_build_samples
+    gtest_build_tests
+    gtest_disable_pthreads
+    gtest_force_shared_crt
+    gtest_hide_internal_symbols)
 else()
   message(STATUS
     "Google Mock was not found - tests based on that will not build")