autowaf has no real shutdown functionality anyway. The automatic
shutdown function that could have been called wouldn't work anyway, as
it takes an argument.
The only reason it doesn't fail is that the top level wscript has no
shutdown handling and doesn't recurse to other scripts, so it is all
dead code.
Variables by these names are only used from the local wscript and when
running "waf configure", which already for other reasons only can run at
the top-level.
These variables are thus not mandatory and not used.
Previously this was inherited via PBD.
On MacOS/X, this adds
"-undefined dynamic_lookup -flat_namespace"
and various "-framework .." options to linkflags
Without this flag, .dylibs fail to link usually because
of missing `-lintl` (Undefined symbols: "_libintl_dgettext")
On other systems this is a NO-OP:
CFLAGS_OSX, CXXFLAGS_OSX and LINKFLAGS_OSX
are only set on the darwin platform.
