perf python: Don't stop building if python setuptools isn't installed

The python3-setuptools package is needed to build the python binding, so
that one can use things like:

  # ~acme/git/perf/tools/perf/python/twatch.py
  cpu: 6, pid: 4573, tid: 2184618 { type: exit, pid: 4573, ppid: 4172, tid: 2184618, ptid: 4172, time: 12563190090107}
  cpu: 24, pid: 4573, tid: 4573 { type: fork, pid: 4573, ppid: 4573, tid: 2190991, ptid: 4573, time: 12563415289331}
  cpu: 29, pid: 4573, tid: 2190991 { type: comm, pid: 4573, tid: 2190991, comm: StreamT~ns #401 }
  cpu: 29, pid: 4573, tid: 2190991 { type: comm, pid: 4573, tid: 2190991, comm: StreamT~ns #401 }
  ^CTraceback (most recent call last):
    File "/var/home/acme/git/perf/tools/perf/python/twatch.py", line 61, in <module>
      main()
    File "/var/home/acme/git/perf/tools/perf/python/twatch.py", line 33, in main
      evlist.poll(timeout = -1)
  KeyboardInterrupt

  #

That have 'import perf;'.

But distros don't always have that python3-setuptools (or equivalent)
installed, which was breaking the build. Just check if it is installed
and emit a warning that such binding isn't being built and continue the
build without it:

With it:

  $ rpm -q python3-setuptools
  python3-setuptools-59.6.0-3.fc36.noarch
  $ rm -rf /tmp/build/perf; mkdir -p /tmp/build/perf
  $ make O=/tmp/build/perf -C tools/perf install-bin
  make: Entering directory '/var/home/acme/git/perf/tools/perf'
  <SNIP>
  ...                               libpython: [ on  ]
  <SNIP>
    GEN     /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so
  <SNIP>
  $ ls -la /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so
  -rwxr-xr-x. 1 acme acme 1609112 Dec 17 11:39 /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so
  $

Without it:

  $ sudo rpm -e python3-setuptools
  $ rm -rf /tmp/build/perf ; mkdir -p /tmp/build/perf
  $ make O=/tmp/build/perf -C tools/perf install-bin
  make: Entering directory '/var/home/acme/git/perf/tools/perf'
  <SNIP>
  ...                               libpython: [ on  ]
  <SNIP>
  $ ls -la /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so
  ls: cannot access '/tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so': No such file or directory
  $

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/Y53XHw3rlsaaUgOs@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: acmel

tools/perf/Makefile.config

@@ -890,8 +890,13 @@ else
       else
          LDFLAGS += $(PYTHON_EMBED_LDFLAGS)
          EXTLIBS += $(PYTHON_EMBED_LIBADD)
-         PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
-         LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
+         PYTHON_SETUPTOOLS_INSTALLED := $(shell $(PYTHON) -c 'import setuptools;' 2> /dev/null && echo "yes" || echo "no")
+         ifeq ($(PYTHON_SETUPTOOLS_INSTALLED), yes)
+           PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
+           LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
+	 else
+           msg := $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent);
+         endif
          CFLAGS += -DHAVE_LIBPYTHON_SUPPORT
          $(call detected,CONFIG_LIBPYTHON)
       endif