[Makefile] How to replace +:= to another way

[Makefile] How to replace +:= to another way



gcc version 4.4.4 20100630 (Red Hat 4.4.4-10) (GCC) (Fedora 12)



Fedora 12 can recognize +:=

But Fedora 17 can't recognize.



Happy := a.o

Happy +:= b.o



gcc version 4.7.2 20120921 (Red Hat 4.7.2-2) (GCC) (Fedora 17)



So Fedora 17 must change another way to do this.



Happy := a.o

Happy := $(Happy) b.o