fix compiler error under FORTIFY_SOURCE=2

frameworks/base/libs/androidfw/ObbFile.cpp:340:5: error: ignoring return value of function declared with warn_unused_result attribute [-Werror,-Wunused-result]
    ftruncate(fd, mFooterStart);
    ^~~~~~~~~ ~~~~~~~~~~~~~~~~
1 error generated.
amake: *** [out/host/linux-x86/obj/STATIC_LIBRARIES/libandroidfw_intermediates/ObbFile.o] Error 1

Change-Id: I7080d64e7a830a10b41c1ebf33c60d32b7c8356e

1 files changed, 3 insertions, 1 deletions

diff --git a/libs/androidfw/ObbFile.cpp b/libs/androidfw/ObbFile.cpp
index 195fa9a..95332a3 100644
--- a/libs/androidfw/ObbFile.cpp
+++ b/libs/androidfw/ObbFile.cpp
@@ -337,7 +337,9 @@ bool ObbFile::removeFrom(int fd)
         return false;
     }
 
-    ftruncate(fd, mFooterStart);
+    if (ftruncate(fd, mFooterStart) == -1) {
+        return false;
+    }
 
     return true;
 }