Fix linker issue on MacOS

The linker on macos ignores "common" symbols, resulting in linker
failures.

We now explicitly initialize the zero buffer to make sure this doesn't
happen. See https://stackoverflow.com/questions/28464770 for details
on why this happens on MacOs.

Bug: b/155459126
Change-Id: Ibf1a8818a9ad2675861883fbbe2c5b7103585004

nasmlib/zerobuf.c

diff --git a/nasmlib/zerobuf.c b/nasmlib/zerobuf.c
index 651c0fd..cb35af5 100644
--- a/nasmlib/zerobuf.c
+++ b/nasmlib/zerobuf.c
@@ -1,5 +1,5 @@
 /* ----------------------------------------------------------------------- *
- *   
+ *
  *   Copyright 1996-2016 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
@@ -14,7 +14,7 @@
  *     copyright notice, this list of conditions and the following
  *     disclaimer in the documentation and/or other materials provided
  *     with the distribution.
- *     
+ *
  *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
@@ -38,5 +38,7 @@
 #include "compiler.h"
 #include "nasmlib.h"
 
-/* Uninitialized -> all zero by C spec */
-const uint8_t zero_buffer[ZERO_BUF_SIZE];
+/* Explicitly initialize buffer, as some linkers will drop common symbols
+  (See https://stackoverflow.com/questions/28464770)
+*/
+const uint8_t zero_buffer[ZERO_BUF_SIZE] = {0};
\ No newline at end of file