bug#22223: multiple '-local' targets in a rule

[Basin Ilya]

If you define a supported `-local` target (e.g. `all-local`) in
`Makefile.am`, `automake` will supplement the standard target (e.g.
`all`) with it.

* https://www.gnu.org/software/automake/manual/html_node/Extending.html
*
https://www.gnu.org/software/automake/manual/html_node/Third_002dParty-Makefiles.html

But this only works, when creating separate rules for `-local` targets.
When listing multiple `-local` target in one rule, they are not applied.

good:

    all-local:
        echo $@

    clean-local:
        echo $@

resulting `Makefile`:

    all-am: Makefile all-local
    clean-am: clean-generic clean-libtool clean-local mostlyclean-am

bad:

    all-local clean-local:
        echo $@

resulting `Makefile`:

    all-am: Makefile
    clean-am: clean-generic clean-libtool mostlyclean-am