Makefile: add and use the ".DELETE_ON_ERROR" flag

Makefile: add and use the ".DELETE_ON_ERROR" flag

Use the GNU make ".DELETE_ON_ERROR" flag in our main Makefile, as we
already do in the Documentation/Makefile since db10fc6c09f (doc:
simplify Makefile using .DELETE_ON_ERROR, 2021-05-21).

Now if a command to make X fails X will be removed, the default
behavior of GNU make is to only do so if "make" itself is interrupted
with a signal.

E.g. if we now intentionally break one of the rules with:

    -       mv $@+ $@
    +       mv $@+ $@ && \
    +       false

We'll get output like:

    $ make git
        CC git.o
        LINK git
    make: *** [Makefile:2179: git] Error 1
    make: *** Deleting file 'git'
    $ file git
    git: cannot open `git' (No such file or directory)

Before this change we'd leave the file in place in under this
scenario.

As in db10fc6c09f this allows us to remove patterns of removing
leftover $@ files at the start of rules, since previous failing runs
of the Makefile won't have left those littered around anymore.

I'm not as confident that we should be replacing the "mv $@+ $@"
pattern entirely, since that means that external programs or one of
our other Makefiles might race and get partial content.

I'm not changing $(REMOTE_CURL_ALIASES) since that uses a ln/ln -s/cp
dance, and would require the addition of "-f" flags if the "rm" at the
start was removed. I've also got plans to fix that ln/ln -s/cp pattern
in another series.

For $(LIB_FILE) and $(XDIFF_LIB) we can rely on the "c" (create) being
present in ARFLAGS.

I'm not changing "$(ETAGS_TARGET)", "tags" and "cscope" because
they've got a messy combination of removing "$@+" not "$@" at the
beginning, or "$@*". I'm also addressing those in another series.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>