Ah I guess it was the line:
```
OBJSXBMC:=$(filter-out $(DYNOBJSXBMC), $(OBJSXBMC))
```
which was likely causing me trouble.  It uses simple expansion rather than recursive.  See http://www.gnu.org/software/make/manual/make.html#Flavors.  I think we're OK if we can get OSX worked out.