[fuchsia] Don't archive symbols for stripped binaries.

Fixes a regression in archive tarball construction which was archiving
stripped binaries in the symbol tarball, as if it was a valid symbol
source.

R=fdegans@chromium.org, frousseau@google.com

Bug: 996050
Change-Id: I329f10a3fc3fdf75f354d537d0923ba1cb670ff1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769545Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Fabrice de Gans-Riberi <fdegans@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690109}

build/config/fuchsia/build_symbol_archive.py

@@ -9,6 +9,7 @@
 
 import argparse
 import os
+import subprocess
 import sys
 import tarfile
 
@@ -40,6 +41,11 @@ def main(args):
         # This is a prebuilt which wasn't accompanied by SDK symbols.
         continue
 
+    # Exclude stripped binaries (indicated by their lack of symbol tables).
+    readelf_output = subprocess.check_output(
+        ['readelf', '-S', symbol_source_path])
+    if not '.symtab' in readelf_output:
+      continue
 
     # Archive the unstripped ELF binary, placing it in a hierarchy keyed to the
     # GNU build ID. The binary resides in a directory whose name is the first