Reflect add execv() and execl()

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

libc/build.mk

@@ -382,6 +382,8 @@ libc += prng/random.o
 
 libc += process/execve.o
 libc += process/execle.o
+libc += process/execv.o
+libc += process/execl.o
 
 libc += arch/$(arch)/setjmp/setjmp.o
 libc += arch/$(arch)/setjmp/longjmp.o