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 <[e-mail]>
Signed-off-by: Jiri Olsa <[e-mail]>
Tested-by: Josh Boyer <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: [e-mail] # v4.2+
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/setup.py

···
 # switch off several checks (need to be at the end of cflags list)
 cflags += ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter' ]
 
+src_perf  = getenv('srctree') + '/tools/perf'
 build_lib = getenv('PYTHON_EXTBUILD_LIB')
 build_tmp = getenv('PYTHON_EXTBUILD_TMP')
 libtraceevent = getenv('LIBTRACEEVENT')
···
 
 ext_sources = [f.strip() for f in file('util/python-ext-sources')
 				if len(f.strip()) > 0 and f[0] != '#']
+
+# use full paths with source files
+ext_sources = map(lambda x: '%s/%s' % (src_perf, x) , ext_sources)
 
 perf = Extension('perf',
 		  sources = ext_sources,