X Force rebuild *.t programs

This makes sure those programs are always built afresh instead being
stuck at outdated build. This is needed because corresponding test .c
file includes many other .c files and we don't implement dependency
tracking.

Makefile

@@ -100,7 +100,7 @@ test.t	: $(TESTS:%=%.trun)
 	#gdb -q -ex run -ex backtrace -ex quit $(XRUN<)
 	$(XRUN<)
 
-%.t	: %.c $(ccan_config)
+%.t	: %.c $(ccan_config) FORCE
 	$(LINKC)
 
 # test with AddressSanitizer