perf tools: Fix python extension build

The util/python-ext-sources file contains source files required to build
the python extension relative to $(srctree)/tools/perf,

Such a file path $(FILE).c is handed over to the python extension build
system, which builds the final object in the
$(PYTHON_EXTBUILD)/tmp/$(FILE).o path.

After the build is done all files from $(PYTHON_EXTBUILD)lib/ are
carried as the result binaries.

Above system fails when we add source file relative to ../lib, which we
do for:

  ../lib/bitmap.c
  ../lib/find_bit.c
  ../lib/hweight.c
  ../lib/rbtree.c

All above objects will be built like:

  $(PYTHON_EXTBUILD)/tmp/../lib/bitmap.c
  $(PYTHON_EXTBUILD)/tmp/../lib/find_bit.c
  $(PYTHON_EXTBUILD)/tmp/../lib/hweight.c
  $(PYTHON_EXTBUILD)/tmp/../lib/rbtree.c

which accidentally happens to be final library path:

  $(PYTHON_EXTBUILD)/lib/

Changing setup.py to pass full paths of source files to Extension build
class and thus keep all built objects under $(PYTHON_EXTBUILD)tmp
directory.

Reported-by: Jeff Bastian <jbastian@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Josh Boyer <jwboyer@fedoraproject.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org # v4.2+
Link: http://lkml.kernel.org/r/20160227201350.GB28494@krava.redhat.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>