Do not use >; in cmd/ast/tools/Makefile
usr/src/cmd/ast/tools/Makefile uses ksh's
>; redirection in an attempt to create the target atomically, and avoid leaving it with partial content.
However, in some circumstances, this does not work and the final rename fails (see #13512).
Note that this does somehow work when running a build with nightly, and often under bldenv (at least in all of the testing I've done for the various ksh changes)
We should just avoid using this construct in the Makefile entirely