Split off AR options in Makefile.in and configure.

Adds ARFLAGS variable for options, where AR is now just the command
name.  So now $(AR) $(ARFLAGS) is used to build the static library.

Makefile.in

@@ -36,7 +36,8 @@ SHAREDLIBV=libz.so.1.2.5.2
 SHAREDLIBM=libz.so.1
 LIBS=$(STATICLIB) $(SHAREDLIBV)
 
-AR=ar rc
+AR=ar
+ARFLAGS=rc
 RANLIB=ranlib
 LDCONFIG=ldconfig
 LDSHAREDLIBC=-lc
@@ -111,7 +112,7 @@ test64: all64
 	-@rm -f foo.gz
 
 libz.a: $(OBJS)
-	$(AR) $@ $(OBJS)
+	$(AR) $(ARFLAGS) $@ $(OBJS)
 	-@ ($(RANLIB) $@ || true) >/dev/null 2>&1
 
 match.o: match.S