we need to delete the target symlink first before we can create it

This solved the issue with symlinks to directories.  The semantic
of `ln -fs' is special if you run it for directories twice, e.g.

mkdir from
ln -sf from to
find . -name from -or -name to
./to
./from

now run it again
ln -sf from to

find . -name from -or -name to
./to
./from
./from/from

ls -l from
total 1
lrwxrwxr-x  1 wosch  devel  4 Oct  6 13:54 from -> from

PR: 222737

share/mk/web.site.mk

@@ -300,6 +300,7 @@ _installlinks:
 		t=$$1; \
 		shift; \
 		${ECHO_CMD} $$t -\> $$l; \
+		${RM} -f $$t; \
 		${LN} -fs $$l $$t; \
 	done )
 .endif