Adding more verbose output for compile time features checking, to ease
up debuging of feature detection failures.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-fbjha6xs5soyaiek8j4142xg@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

The `try-cc' user-defined function was in tools/perf/feature-tests.mak;
this commit moves it to tools/perf/config/utilities.mak.
Signed-off-by: Michael Witten <mfwitten@gmail.com>
Link: http://lkml.kernel.org/n/tip-bqhwcuxsrve0iodn6q4ejaoi@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Currently, Python 3 is not supported by perf's code; this
can cause the build to fail for systems that have Python 3
installed as the default python:

  python{,-config}

The Correct Solution is to write compatibility code so that
Python 3 works out-of-the-box.

However, users often have an ancillary Python 2 installed:

  python2{,-config}

Therefore, a quick fix is to allow the user to specify those
ancillary paths as the python binaries that Makefile should
use, thereby avoiding Python 3 altogether; as an added benefit,
the Python binaries may be installed in non-standard locations
without the need for updating any PATH variable.

This commit adds the ability to set PYTHON and/or PYTHON_CONFIG
either as environment variables or as make variables on the
command line; the paths may be relative, and usually only PYTHON
is necessary in order for PYTHON_CONFIG to be defined implicitly.
Some rudimentary error checking is performed when the user
explicitly specifies a value for any of these variables.

In addition, this commit introduces significantly robust makefile
infrastructure for working with paths and communicating with the
shell; it's currently only used for handling Python, but I hope
it will prove useful in refactoring the makefiles.

Thanks to:

  Raghavendra D Prabhu <rprabhu@wnohang.net>

for motivating this patch.
Acked-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
Link: http://lkml.kernel.org/r/e987828e-87ec-4973-95e7-47f10f5d9bab-mfwitten@gmail.comSigned-off-by: Michael Witten <mfwitten@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>