silo: Build with -U_FORTIFY_SOURCE

Otherwise the build will fail:

| ld: decompnet.o: in function `error':
| decomp.c:(.text+0x4dc): undefined reference to `__longjmp_chk'

Signed-off-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Rules.make b/Rules.make
index 3d0efe7..9739f7a 100644
--- a/Rules.make
+++ b/Rules.make
@@ -19,7 +19,8 @@
 		> /dev/null 2>&1; then echo "y"; else echo "n"; fi;)
 
 CFLAGS = -Os -Wall -I. -I../include -fomit-frame-pointer \
-	-fno-strict-aliasing -fno-PIC -DSMALL_RELOC=$(SMALL_RELOC) \
+	-fno-strict-aliasing -fno-PIC -U_FORTIFY_SOURCE \
+	-DSMALL_RELOC=$(SMALL_RELOC) \
 	-DLARGE_RELOC=$(LARGE_RELOC)
 HOSTCFLAGS = -O2 -Wall