Gmake: Implicit rule for archives and variable as prerequisit

[Pascal MALAISE]

Hi,

I am using a "generic" makefile defining implicit rules so that it can 
be included by several makefiles in several directories.
I have a problem for generating archives (.a and .so).

Here is the makefile in the target dir. The idea is to define the list 
of archives and, for each archive, the list of objects to store in it.
------------------------------------------
# Example of makefile
LIBS := lib

OBJS_lib := test.o

include c.mk
-------------------------------------------
# Generic makefile for use in several projects
# c.mk
.SUFFIXES : .c .o .a
.PHONY : all

ALIBS  := $(LIBS:%=%.a)

%.o : %.c
        touch $@

%.a :
        ar crvs $@ $(OBJS_$(@F:%.a=%))

all : $(ALIBS)
---------------------------------------------

This can be tested after creating a dummy test.c, then calling make
ar crvs lib.a test.o
ar: test.o: No such file or directory

The only solution I have found is to append (after the include) in each 
makefile:
lib.a : $(OBJS_lib)
Then, "make" knows that for lib.a and %.a implicit rule, test_x.o is a 
prerequisit.
I would like to move this explicit definition that "lib.a" needs 
$(OBJS_lib), in the implicit part of the scheme.

I have tried %.a : $(OBJS_$(@F:%.a=%)) in the implicit rule but this 
does not work because: "Note that expansion using `%' in pattern rules 
occurs after any variable or function expansions", so @F expands 
probably to "%a".

Is there a nice way to write an implicite rule for an archive, using a 
variable for defining the list of prerequisits?
Or is there a different way (using archive features from §11) to solve 
this problem?

Thank's in advance