waf: parse LDFLAGS from python

waf: parse LDFLAGS from python

The LDFLAGS returned by get_python_variables may contain additional library
search paths. These need to be parsed out and placed in LIBPATH to maintain
correct ordering of search paths in the final link flags.

Specifically, appending LDFLAGS directly to LINKFLAGS on my system was causing
/usr/lib to be the first search path specified. This lead to linking against
installed libraries rather than the versions from the current build.

Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Oct 25 02:48:35 CEST 2013 on sn-devel-104