build: fix incremental building Running `make; touch *.c; make` fails because the symlinks already exist, and creating them again fails: ln: failed to create symbolic link '.../rootdev/librootdev.so.1': File exists make: *** [Makefile:20: .../rootdev/librootdev.so.1.0] Error 1 Add flags to force recreate/clobber the symlinks to fix. BUG=None TEST=`make; touch *.c; make` works Change-Id: I67368c9446e6c59a83e1e9ca6976ea2039e93751 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/rootdev/+/5545939 Auto-Submit: Mike Frysinger <[email protected]> Reviewed-by: Brian Norris <[email protected]> Tested-by: Mike Frysinger <[email protected]> Commit-Queue: Brian Norris <[email protected]>