Land a fork of Fuchsia's elfinfo.py, and update runner_common to use it.

elfinfo.py is a direct fork of mcgrathr@'s implementation:
https://fuchsia.googlesource.com/packages/+/master/gn/elfinfo.py

For simplicity the runner script now uses elfinfo to strip binaries
regardless of the target architecture.

Bug: 773444
Change-Id: Ic9dcc0298b69da05dcea1e178c3539bdfa1dccbe
Reviewed-on: https://chromium-review.googlesource.com/750238
Commit-Queue: Wez <wez@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Reviewed-by: Roland McGrath <mcgrathr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517251}

build/config/fuchsia/rules.gni

@@ -50,6 +50,7 @@ template("generate_runner_script") {
     ]
     data += [
       invoker.generated_script,
+      "//build/fuchsia/elfinfo.py",
       "//build/fuchsia/exe_runner.py",
       "//build/fuchsia/test_runner.py",
       "//build/fuchsia/runner_common.py",

build/fuchsia/runner_common.py

@@ -20,6 +20,8 @@ import tarfile
 import time
 import uuid
 
+import elfinfo
+
 
 DIR_SOURCE_ROOT = os.path.abspath(
     os.path.join(os.path.dirname(__file__), os.pardir, os.pardir))
@@ -138,9 +140,11 @@ def _StripBinary(dry_run, bin_path):
   """Creates a stripped copy of the executable at |bin_path| and returns the
   path to the stripped copy."""
   strip_path = bin_path + '.bootfs_stripped'
-  _RunAndCheck(dry_run, ['/usr/bin/strip', bin_path, '-o', strip_path])
-  if not dry_run and not os.path.exists(strip_path):
-    raise Exception('strip did not create output file')
+  if dry_run:
+    print "Strip", bin_path, " to ", strip_path
+  else:
+    info = elfinfo.get_elf_info(bin_path)
+    info.strip(strip_path)
   return strip_path
 
 
@@ -155,8 +159,6 @@ def _StripBinaries(dry_run, file_mapping, target_cpu):
       file_tag = f.read(4)
     if file_tag == '\x7fELF':
       symbols_mapping[target] = source
-      # TODO(wez): Strip ARM64 binaries as well. See crbug.com/773444.
-      if target_cpu == 'x64':
       file_mapping[target] = _StripBinary(dry_run, source)
   return symbols_mapping