build

Add the missing `migrate_weights` target for CMake #3260

Job	Run time
bazel	1m 17s
macos-latest (make) Release	1m 3s
ubuntu-20.04 (make) Release	1m 24s
ubuntu-latest (make) Release	1m 12s
windows-latest (windows) Release	15m 57s
	20m 53s

Provide feedback