[PATCH v2 0/8] Makefile: optimize noop runs, add shared.mak

As the v1 notes (among other things): https://lore.kernel.org/git/cover-0.8-00000000000-20211217T012902Z-avarab@gmail.com/

    This speeds up noop runs of "make" by a lot. After a "make" running a
    "make -j1" with this is ~1.5 faster than on "master"[2], and around 3x
    as fast with "make -j1 NO_TCLTK=Y" (the TCL part takes a lot of time,
    but that's another matter).

This v2 re-roll addresses trivial commit message/comment grammar/typo issues pointed out by Eric Sunshine, thanks Eric!

Ævar Arnfjörð Bjarmason (8):
  Makefiles: add "shared.mak", move ".DELETE_ON_ERROR" to it
  Makefile: disable GNU make built-in wildcard rules
  Makefile: define $(LIB_H) in terms of $(FIND_SOURCE_FILES)
  Makefile: move ".SUFFIXES" rule to shared.mak
  Makefile: move $(comma), $(empty) and $(space) to shared.mak
  Makefile: add "$(QUIET)" boilerplate to shared.mak
  Makefile: use $(wspfx) for $(QUIET...) in shared.mak
  Makefiles: add and use wildcard "mkdir -p" template

 Documentation/Makefile |  63 +++-------------------
 Makefile               | 118 +++++++++++++----------------------------
 config.mak.uname       |   1 -
 shared.mak             | 109 +++++++++++++++++++++++++++++++++++++
 t/Makefile             |   3 ++
 t/interop/Makefile     |   3 ++
 templates/Makefile     |   8 ++-
 7 files changed, 160 insertions(+), 145 deletions(-)
 create mode 100644 shared.mak

Range-diff against v1:
1:  f74b47662b7 = 1:  b652fc78fda Makefiles: add "shared.mak", move ".DELETE_ON_ERROR" to it
2:  b0c63abe091 = 2:  b0c9be581a6 Makefile: disable GNU make built-in wildcard rules
3:  c6c6f7cf8d8 = 3:  ed6fd1c0bd1 Makefile: define $(LIB_H) in terms of $(FIND_SOURCE_FILES)
4:  ed64cd1bd4a = 4:  4c6d8089fff Makefile: move ".SUFFIXES" rule to shared.mak
5:  1749085b929 = 5:  f1f02c71dbc Makefile: move $(comma), $(empty) and $(space) to shared.mak
6:  c25284b24cf = 6:  fb877060d6b Makefile: add "$(QUIET)" boilerplate to shared.mak
7:  3daef7672be = 7:  90d804ea9a0 Makefile: use $(wspfx) for $(QUIET...) in shared.mak
8:  aca560ca410 ! 8:  59c1b7032db Makefiles: add and use wildcard "mkdir -p" template
    @@ Commit message
     
         But as it turns out we can use this neat trick of only doing a "mkdir
         -p" if the $(wildcard) macro tells us the path doesn't exist. A re-run
    -    of a performance test similar to thatnoted downthread of [1] in [2]
    +    of a performance test similar to that noted downthread of [1] in [2]
         shows that this is faster, in addition to being less verbose and more
         reliable (this uses my "git-hyperfine" thin wrapper for "hyperfine"[3]):
     
    @@ shared.mak: ifndef V
     +## needed.
     +##
     +## Is racy, but in a good way; we might redundantly (and safely)
    -+## "mkdir -p" when running in parallel, but won't need to exhaustively
    ++## "mkdir -p" when running in parallel, but won't need to exhaustively create
     +## individual rules for "a" -> "prefix" -> "dir" -> "file" if given a
     +## "a/prefix/dir/file". This can instead be inserted at the start of
     +## the "a/prefix/dir/file" rule.