Add rule in new Makefile "tests/Makefile.tests" for running shellcheck
on shell test scripts. This automates below shellcheck into the build.

	$ for F in $(find tests/shell/ -perm -o=x -name '*.sh'); do shellcheck -S warning $F; done

Condition for shellcheck is added in Makefile.perf to avoid build
breakage in the absence of shellcheck binary. Update Makefile.perf to
contain new rule for "SHELLCHECK_TEST" which is for making shellcheck
test as a dependency on perf binary.

Added "tests/Makefile.tests" to run shellcheck on shellscripts in
tests/shell. The make rule "SHLLCHECK_RUN" ensures that, every time
during make, shellcheck will be run only on modified files during
subsequent invocations. By this, if any newly added shell scripts or
fixes in existing scripts breaks coding/formatting style, it will get
captured during the perf build.

Example build failure by modifying probe_vfs_getname.sh in tests/shell:

	In tests/shell/probe_vfs_getname.sh line 8:
	. $(dirname $0)/lib/probe.sh
	  ^-----------^ SC2046 (warning): Quote this to prevent word splitting.

	For more information:
	  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
	make[3]: *** [/root/athira/perf-tools-next/tools/perf/tests/Makefile.tests:18: tests/shell/.probe_vfs_getname.sh.shellcheck_log] Error 1
	make[2]: *** [Makefile.perf:686: SHELLCHECK_TEST] Error 2
	make[2]: *** Waiting for unfinished jobs....
	make[1]: *** [Makefile.perf:244: sub-make] Error 2
	make: *** [Makefile:70: all] Error 2

Here, like other files which gets created during compilation (ex:
.builtin-bench.o.cmd or .perf.o.cmd ), create .shellcheck_log also as a
hidden file.  Example: tests/shell/.probe_vfs_getname.sh.shellcheck_log
shellcheck is re-run if any of the script gets modified based on its
dependency of this log file.

After this, for testing, changed "tests/shell/trace+probe_vfs_getname.sh" to
break shellcheck format. In the next make run, it is also captured:

	In tests/shell/probe_vfs_getname.sh line 8:
	. $(dirname $0)/lib/probe.sh
	  ^-----------^ SC2046 (warning): Quote this to prevent word splitting.

	For more information:
	  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
	make[3]: *** [/root/athira/perf-tools-next/tools/perf/tests/Makefile.tests:18: tests/shell/.probe_vfs_getname.sh.shellcheck_log] Error 1
	make[3]: *** Waiting for unfinished jobs....

	In tests/shell/trace+probe_vfs_getname.sh line 14:
	. $(dirname $0)/lib/probe.sh
	  ^-----------^ SC2046 (warning): Quote this to prevent word splitting.

	For more information:
	  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
	make[3]: *** [/root/athira/perf-tools-next/tools/perf/tests/Makefile.tests:18: tests/shell/.trace+probe_vfs_getname.sh.shellcheck_log] Error 1
	make[2]: *** [Makefile.perf:686: SHELLCHECK_TEST] Error 2
	make[2]: *** Waiting for unfinished jobs....
	make[1]: *** [Makefile.perf:244: sub-make] Error 2
	make: *** [Makefile:70: all] Error 2

Failure log can be found in the stdout of make itself.

This is reported at build time. To be able to go ahead with the build or
disable shellcheck even though it is known that some test is broken, add
a "NO_SHELLCHECK" option. Example:

  make NO_SHELLCHECK=1

	  INSTALL libsubcmd_headers
	  INSTALL libsymbol_headers
	  INSTALL libapi_headers
	  INSTALL libperf_headers
	  INSTALL libbpf_headers
	  LINK    perf

Note:

This is tested on RHEL and also SLES. Use below check:
"$(shell which shellcheck 2> /dev/null)" to look for presence
of shellcheck binary. The approach "shell command -v" is not
used here. In some of the distros(RHEL), command is available
as executable file (/usr/bin/command). But in some distros(SLES),
it is a shell builtin and not available as executable file.

Committer testing:

  $ type shellcheck
  shellcheck is hashed (/usr/bin/shellcheck)
  $ rpm -qf /usr/bin/shellcheck
  ShellCheck-0.9.0-2.fc38.x86_64
  $
  $ alias m
  $ git diff
  diff --git a/tools/perf/tests/shell/probe_vfs_getname.sh b/tools/perf/tests/shell/probe_vfs_getname.sh
  index 554e12e83c55fd56..dbc14634678e2bf6 100755
  --- a/tools/perf/tests/shell/probe_vfs_getname.sh
  +++ b/tools/perf/tests/shell/probe_vfs_getname.sh
  @@ -5,7 +5,7 @@
   # Arnaldo Carvalho de Melo <acme@kernel.org>, 2017

   # shellcheck source=lib/probe.sh
  -. "$(dirname $0)"/lib/probe.sh
  +. $(dirname $0)/lib/probe.sh

   skip_if_no_perf_probe || exit 2

  alias m='rm -rf ~/libexec/perf-core/ ; make -k CORESIGHT=1 O=/tmp/build/$(basename $PWD) -C tools/perf install-bin && perf test python'
  $ m
  make: Entering directory '/home/acme/git/perf-tools-next/tools/perf'
    BUILD:   Doing 'make -j32' parallel build
<SNIP>
    INSTALL libbpf_headers

  In tests/shell/probe_vfs_getname.sh line 8:
  . $(dirname $0)/lib/probe.sh
    ^-----------^ SC2046 (warning): Quote this to prevent word splitting.

  For more information:
    https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
  make[3]: *** [/home/acme/git/perf-tools-next/tools/perf/tests/Makefile.tests:18: tests/shell/.probe_vfs_getname.sh.shellcheck_log] Error 1
  make[2]: *** [Makefile.perf:686: SHELLCHECK_TEST] Error 2
  make[2]: *** Waiting for unfinished jobs....
  make[1]: *** [Makefile.perf:244: sub-make] Error 2
  make: *** [Makefile:113: install-bin] Error 2
  make: Leaving directory '/home/acme/git/perf-tools-next/tools/perf'
  $
Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20231123160232.94253-1-atrajeev@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>