Fix file descriptor leak when opening invalid archives.

Also add -Wunreachable-code to the set of compiler flags, otherwise
noreturn becomes considerably less useful.

bug: https://code.google.com/p/android/issues/detail?id=171099
Change-Id: I9a95d45633c731c7046d4e4a39844d9cebfd1718
(cherrypick of 241bcf05e0e394bbf2681f359f52646dd6c707f6.)
diff --git a/fastboot/Android.mk b/fastboot/Android.mk
index 1808042..66a470a 100644
--- a/fastboot/Android.mk
+++ b/fastboot/Android.mk
@@ -25,7 +25,7 @@
 LOCAL_MODULE := fastboot
 LOCAL_MODULE_TAGS := debug
 LOCAL_CONLYFLAGS += -std=gnu99
-LOCAL_CFLAGS += -Wall -Wextra -Werror
+LOCAL_CFLAGS += -Wall -Wextra -Werror -Wunreachable-code
 
 LOCAL_CFLAGS += -DFASTBOOT_REVISION='"$(fastboot_version)"'