Use $(MAKE), not make

For the sake of systems where we want gmake.
diff --git a/programs/Makefile b/programs/Makefile
index f62e2c6..26aaa8b 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -81,7 +81,7 @@
 all: $(APPS)
 
 $(DEP):
-	make -C ../library
+	$(MAKE) -C ../library
 
 aes/aescrypt2$(EXEXT): aes/aescrypt2.c $(DEP)
 	echo   "  CC    aes/aescrypt2.c"