Fix GN os, cpu defaults for Android builds.

tools/relocation_packer/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("config.gni")
 import("//testing/test.gni")
 
 assert(relocation_packing_supported)
 
-if (target_arch == "arm") {
+if (target_cpu == "arm") {
   target_define = "TARGET_ARM"
-} else if (target_arch == "arm64") {
+} else if (target_cpu == "arm64") {
   target_define = "TARGET_ARM64"
 }
 
 if (current_toolchain == host_toolchain) {
   # GYP: //tools/relocation_packer/relocation_packer.gyp:lib_relocation_packer
   source_set("lib_relocation_packer") {
     defines = [ target_define ]
     deps = [
       "//third_party/elfutils:libelf",
     ]
@@ skipping 48 matching lines @@
     include_dirs = [ "//" ]
     deps = [
       ":lib_relocation_packer",
       ":relocation_packer_test_data",
       "//testing:gtest",
     ]
   }
 }
 
 if (current_toolchain == default_toolchain &&
-    (target_arch == "arm" || target_arch == "arm64")) {
+    (target_cpu == "arm" || target_cpu == "arm64")) {
   # Targets to build test data.  These participate only in building test
   # data for use with elf_file_unittest.cc, and are not part of the main
   # relocation packer build.  Unit test data files are checked in to the
   # source tree as 'golden' data, and are not generated 'on the fly' by
   # the build.
   #
   # See test_data/generate_elf_file_unittest_relocs.sh for instructions.
 
   # GYP: //tools/relocation_packer/relocation_packer.gyp:relocation_packer_test_data
   shared_library("relocation_packer_test_data") {
     cflags = [
       "-O0",
       "-g0",
     ]
     sources = [
       "test_data/elf_file_unittest_relocs.cc",
     ]
   }
 
   # GYP: //tools/relocation_packer/relocation_packer.gyp:relocation_packer_unittests_test_data
   action("relocation_packer_unittests_test_data") {
     script = "test_data/generate_elf_file_unittest_relocs.py"
     test_file = "$root_build_dir/librelocation_packer_test_data.so"
-    if (target_arch == "arm") {
+    if (target_cpu == "arm") {
       added_section = ".android.rel.dyn"
       packed_output = "elf_file_unittest_relocs_arm32_packed.so"
       unpacked_output = "elf_file_unittest_relocs_arm32.so"
-    } else if (target_arch == "arm64") {
+    } else if (target_cpu == "arm64") {
       added_section = ".android.rela.dyn"
       packed_output = "elf_file_unittest_relocs_arm64_packed.so"
       unpacked_output = "elf_file_unittest_relocs_arm64.so"
     } else {
       assert(false, "Unsupported target arch for relocation packer")
     }
 
     packed_output = "$root_build_dir/$packed_output"
     unpacked_output = "$root_build_dir/$unpacked_output"
 
@@ skipping 19 matching lines @@
       "--added-section=$added_section",
       "--test-file",
       rebase_path(test_file, root_build_dir),
       "--packed-output",
       rebase_path(packed_output, root_build_dir),
       "--unpacked-output",
       rebase_path(unpacked_output, root_build_dir),
     ]
   }
 }