hwloc: correctly handle --with-hwloc=external

- simply #include "hwloc.h" to use the external hwloc header
- do use the external hwloc header instead of opal/mca/hwloc/hwloc.h

Thanks Orion Poplawski for the report

Fixes open-mpi/ompi#2616

Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>

opal/mca/hwloc/Makefile.am

@@ -1,5 +1,7 @@
 #
 # Copyright (c) 2011      Cisco Systems, Inc.  All rights reserved.
+# Copyright (c) 2016      Research Organization for Information Science
+#                         and Technology (RIST). All rights reserved.
 # $COPYRIGHT$
 #
 # Additional copyrights may follow
@@ -7,6 +9,11 @@
 # $HEADER$
 #
 
+# we do not want -I$(srcdir) in DEFAULT_INCLUDES
+# otherwise there can be a conflict between system hwloc.h and opal/mca/hwloc/hwloc.h
+# so just hack DEFAULT_INCLUDES with only what we need
+DEFAULT_INCLUDES = -I$(top_builddir)/opal/include
+
 # main library setup
 noinst_LTLIBRARIES = libmca_hwloc.la
 libmca_hwloc_la_SOURCES =

opal/mca/hwloc/external/configure.m4

@@ -1,7 +1,7 @@
 # -*- shell-script -*-
 #
 # Copyright (c) 2009-2016 Cisco Systems, Inc.  All rights reserved.
-# Copyright (c) 2014      Research Organization for Information Science
+# Copyright (c) 2014-2016 Research Organization for Information Science
 #                         and Technology (RIST). All rights reserved.
 #
 # $COPYRIGHT$
@@ -61,12 +61,17 @@ AC_DEFUN([MCA_opal_hwloc_external_POST_CONFIG],[
            # OPAL_HWLOC_WANT_VERBS_HELPER is set, that file will
            # include the external hwloc/openfabrics-verbs.h file (via
            # the MCA_hwloc_external_openfabrics_helper define).
+           AS_IF([test "$opal_hwloc_dir" != ""],
+                 [opal_hwloc_include="$opal_hwloc_dir/include/hwloc.h"
+                  opal_hwloc_openfabrics_include="$opal_hwloc_dir/include/hwloc/hwloc/openfabrics-verbs.h"],
+                 [opal_hwloc_include="hwloc.h"
+                  opal_hwloc_openfabrics_include="hwloc/openfabrics-verbs.h"])
            AC_DEFINE_UNQUOTED(MCA_hwloc_external_header,
-                  ["$opal_hwloc_dir/include/hwloc.h"],
+                  ["$opal_hwloc_include"],
                   [Location of external hwloc header])
            AC_DEFINE_UNQUOTED(MCA_hwloc_external_openfabrics_header,
-                  ["$opal_hwloc_dir/include/hwloc/openfabrics-verbs.h"],
-                  [Location of external hwloc header])
+                  ["$opal_hwloc_openfabrics_include"],
+                  [Location of external hwloc openfabrics header])
           ])
     OPAL_VAR_SCOPE_POP
 ])dnl