Fix bug #771615

--- a/bin/Makefile	2024-04-11 08:00:24.832420892 +0200
+++ b/bin/Makefile	2024-04-11 07:59:56.052410291 +0200
@@ -152,7 +152,7 @@
 	$(INSTALLCMD) pplot $(BINDIR)

 blu: blu.o profil.o
-	$(FC) -o blu blu.o profil.o
+	$(FC) -o blu blu.o profil.o $(FTNLIB)
 	$(INSTALLCMD) blu $(BINDIR)