[build Folder Migration] Move build/executorch-config.cmake (pytorch#9318)

### Summary
A series of diffs as a part of
pytorch#9117.

### Test plan

CI

cc @larryliu0820 @lucylq

Author: jathu

CMakeLists.txt

@@ -682,7 +682,7 @@ install(
   INCLUDES
   DESTINATION ${_common_include_directories}
 )
-install(FILES build/executorch-config.cmake DESTINATION lib/cmake/ExecuTorch)
+install(FILES tools/cmake/executorch-config.cmake DESTINATION lib/cmake/ExecuTorch)
 
 #
 # executor_runner: Host tool that demonstrates program execution.