perf tools: Stop depending on .git files for building PERF-VERSION-FILE

This essentially reverts commit c72e3f04 ("tools/perf/build:
Speed up git-version test on re-make") and commit 4e666cdb
("perf tools: Fix dependency for version file creation")

In commit c72e3f04 ("tools/perf/build: Speed up git-version test
on re-make"), a makefile dependency on .git/HEAD was added. The
background is that running PERF-VERSION-FILE is relatively slow, and
commands like "git describe" are particularly slow.

In commit 4e666cdb ("perf tools: Fix dependency for version file
creation"), an additional dependency on .git/ORIG_HEAD was added, as
.git/HEAD may not change for "git reset --hard HEAD^" command. However,
depending on whether we're on a branch or not, a "git cherry-pick" may
not lead to the version being updated.

As discussed with the git community in [0], using git internal files for
dependencies is not reliable. Commit 4e666cdb also breaks some build
scenarios [1].

As mentioned, c72e3f04 ("tools/perf/build: Speed up git-version
test on re-make") was added to speed up the build. However in commit
7572733b ("perf tools: Fix version kernel tag") we removed the
call to "git describe", so just revert Makefile.perf back to same as pre
c72e3f04 ("tools/perf/build: Speed up git-version test on
re-make") and the build should not be so slow, as below:

Pre 7572733b:

  $> time util/PERF-VERSION-GEN
    PERF_VERSION = 5.17.rc8.g4e666cdb

  real    0m0.110s
  user    0m0.091s
  sys     0m0.019s

Post 7572733b:

  $> time util/PERF-VERSION-GEN
    PERF_VERSION = 5.17.rc8.g7572733b

  real    0m0.039s
  user    0m0.036s
  sys     0m0.007s

[0] https://lore.kernel.org/git/87wngkpddp.fsf@igel.home/T/#m4a4dd6de52fdbe21179306cd57b3761eb07f45f8
[1] https://lore.kernel.org/linux-perf-users/20220329093120.4173283-1-matthieu.baerts@tessares.net/T/#u

Committer testing:

After a fresh rebuild using 'make -C tools/perf O=/tmp/build/perf install-bin':

  $ perf -v
  perf version 5.17.g162f9db407b6
  $ git log --oneline -1
  162f9db407b6a6e5 (HEAD -> perf/core) perf tools: Stop depending on .git files for building PERF-VERSION-FILE
  $

Now using a detached tarball, i.e. outside the kernel source tree:

  $ ls -la perf*tar
  ls: cannot access 'perf*tar': No such file or directory
  $ make perf-tar-src-pkg
    TAR
    PERF_VERSION = 5.17.g31d10b3ef133
  $ ls -la perf*tar
  -rw-r--r--. 1 acme acme 22241280 Mar 30 13:26 perf-5.17.0.tar
  $ mv perf-5.17.0.tar /tmp
  $ cd /tmp
  $ tar xf perf-5.17.0.tar
  $ cd perf-5.17.0/
  $ make -C tools/perf |& tail
    CC      util/pmu.o
    CC      util/pmu-flex.o
    CC      util/expr-flex.o
    CC      util/expr.o
    LD      util/scripting-engines/perf-in.o
    LD      util/intel-pt-decoder/perf-in.o
    LD      util/perf-in.o
    LD      perf-in.o
    LINK    perf
  make: Leaving directory '/tmp/perf-5.17.0/tools/perf'
  $ tools/perf/perf -v
  perf version 5.17.g31d10b3ef133
  $ pwd
  /tmp/perf-5.17.0
  $ cat PERF-VERSION-FILE
  #define PERF_VERSION "5.17.g31d10b3ef133"
  $

Fixes: 4e666cdb ("perf tools: Fix dependency for version file creation")
Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/1648635774-14581-1-git-send-email-john.garry@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile.perf

@@ -691,9 +691,8 @@ $(OUTPUT)common-cmds.h: $(wildcard Documentation/perf-*.txt)
 $(SCRIPTS) : % : %.sh
 	$(QUIET_GEN)$(INSTALL) '$@.sh' '$(OUTPUT)$@'
 
-$(OUTPUT)PERF-VERSION-FILE: ../../.git/HEAD ../../.git/ORIG_HEAD
+$(OUTPUT)PERF-VERSION-FILE: .FORCE-PERF-VERSION-FILE
 	$(Q)$(SHELL_PATH) util/PERF-VERSION-GEN $(OUTPUT)
-	$(Q)touch $(OUTPUT)PERF-VERSION-FILE
 
 # These can record PERF_VERSION
 perf.spec $(SCRIPTS) \
@@ -1139,21 +1138,12 @@ else
 	@echo "FEATURE-DUMP file available in $(OUTPUT)FEATURE-DUMP"
 endif
 
-#
-# Trick: if ../../.git does not exist - we are building out of tree for example,
-# then force version regeneration:
-#
-ifeq ($(wildcard ../../.git/HEAD),)
-    GIT-HEAD-PHONY = ../../.git/HEAD ../../.git/ORIG_HEAD
-else
-    GIT-HEAD-PHONY =
-endif
 
 FORCE:
 
 .PHONY: all install clean config-clean strip install-gtk
 .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell
-.PHONY: $(GIT-HEAD-PHONY) TAGS tags cscope FORCE prepare
+.PHONY: .FORCE-PERF-VERSION-FILE TAGS tags cscope FORCE prepare
 .PHONY: libtraceevent_plugins archheaders
 
 endif # force_fixdep