clean up FORTIFY_SOURCE handling.

Avoid duplicating huge chunks of code.

Change-Id: Id6145cdfce781c5ffba2abaaa79681d25a7ab28f
diff --git a/libc/bionic/__vsnprintf_chk.cpp b/libc/bionic/__vsnprintf_chk.cpp
index b4f534b..95d4915 100644
--- a/libc/bionic/__vsnprintf_chk.cpp
+++ b/libc/bionic/__vsnprintf_chk.cpp
@@ -51,9 +51,7 @@
         va_list va)
 {
     if (supplied_size > dest_len_from_compiler) {
-        __libc_android_log_print(ANDROID_LOG_FATAL, "libc",
-            "*** vsnprintf buffer overflow detected ***\n");
-        abort();
+        __fortify_chk_fail("vsnprintf buffer overflow", 0);
     }
 
     return vsnprintf(dest, supplied_size, format, va);