[PATCH 0/3] Makefile: make "sparse" and "hdr-check" non-.PHONY

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Now that my series to only build "TAGS" when we strictly need to has
landed in 1b8bd2243e7 (Merge branch 'ab/make-tags-cleanup',
2021-09-20), let's do the same for the "sparse" and "hdr-check"
targets.

For *.c files we'll now generate corresponding empty *.sp and *.hco
files when "sparse" and "hdr-check" are run, respectively. If either
of those errored on the *.c file we'd fail to refresh the
corresponding generated file.

Put together a:

    make -j8 all TAGS sparse hdr-check

Takes around 15s on "master" when there's nothing new to do (we re-do
all of "sparse hdr-check"), now it'll take <100ms if there's nothing
to do, and say ~2s if I do a "touch ref*.[ch]".

Ævar Arnfjörð Bjarmason (3):
  Makefile: make the "sparse" target non-.PHONY
  Makefile: do one append in %.hcc rule
  Makefile: make the "hdr-check" target non-.PHONY

 .gitignore |  2 ++
 Makefile   | 21 +++++++++++++--------
 2 files changed, 15 insertions(+), 8 deletions(-)

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2.33.0.1098.gf02a64c1a2d