configure: restore hwloc support

If the pkg-config check for hwloc succeeds, actually define
HAVE_LIBHWLOC to enable the conditional code.

Fixes: 4ccad46 ("configure.ac: fix static build with hwloc")

configure.ac

@@ -479,7 +479,9 @@ case "$enable_hwloc" in
       m4_ifdef([PKG_PROG_PKG_CONFIG], [
          PKG_PROG_PKG_CONFIG()
          PKG_CHECK_MODULES(HWLOC, hwloc, [
-               CFLAGS="$CFLAGS $HWLOC_CFLAGS" LIBS="$LIBS $HWLOC_LIBS"
+               CFLAGS="$CFLAGS $HWLOC_CFLAGS"
+               LIBS="$LIBS $HWLOC_LIBS"
+               AC_DEFINE([HAVE_LIBHWLOC], [1], [Define to 1 if you have the `hwloc' library (-lhwloc).])
             ], [
                AC_CHECK_LIB([hwloc], [hwloc_get_proc_cpubind], [], [AC_MSG_ERROR([can not find required library libhwloc])])
                AC_CHECK_HEADERS([hwloc.h], [], [AC_MSG_ERROR([can not find require header file hwloc.h])])