wasi-sdk-sysroot.cmake: Avoid modifying things out of CMAKE_INSTALL_PREFIX

cmake/wasi-sdk-sysroot.cmake

@@ -246,9 +246,14 @@ endforeach()
 install(DIRECTORY ${wasi_tmp_install}/share
         USE_SOURCE_PERMISSIONS
         DESTINATION ${CMAKE_INSTALL_PREFIX})
-install(DIRECTORY ${wasi_resource_dir}/lib
+cmake_path(IS_PREFIX CMAKE_INSTALL_PREFIX ${clang_resource_dir} NORMALIZE install_resource_dir)
+if(install_resource_dir)
+  install(DIRECTORY ${wasi_resource_dir}/lib
           USE_SOURCE_PERMISSIONS
           DESTINATION ${clang_resource_dir})
+else()
+  message(STATUS "The resource dir (${clang_resource_dir}) will not be updated by the install target because it's out of CMAKE_INSTALL_PREFIX ${CMAKE_INSTALL_PREFIX}")
+endif()
 
 # Add a top-level `build` target as well as `build-$target` targets.
 add_custom_target(build ALL)