For Darwin, export EXE (needed by Lib/plat-generic/regen checkin, to

follow).  Adapted from a patch by Tony Lownds. (#101816)

Makefile.in

@@ -336,6 +336,7 @@ $(srcdir)/Lib/$(PLATDIR):
 		cp $(srcdir)/Lib/plat-generic/regen $(srcdir)/Lib/$(PLATDIR)/regen
 		export PATH; PATH="`pwd`:$$PATH"; \
 		export PYTHONPATH; PYTHONPATH="`pwd`/Lib"; \
+		export EXE; EXE="$(EXE)"; \
 		cd $(srcdir)/Lib/$(PLATDIR); ./regen
 
 # Install the include files