[gn] Switch arm cross-compile bots to gn

[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true

Committed: https://crrev.com/9f42d6c2c021a772362f8db26cb705c672a38a7b
Cr-Commit-Position: refs/heads/master@{#39367}

[Michael Achenbach, 2016-09-12 13:26:48]

Description was changed from

==========
[gn] Switch arm cross-compile bots to gn

BUG=
==========

to

==========
[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true
==========

[Michael Achenbach, 2016-09-12 14:23:49]

machenbach@chromium.org changed reviewers:
+ jochen@chromium.org, vogelheim@chromium.org

[Michael Achenbach, 2016-09-12 14:23:50]

PTAL

Comparison:
https://build.chromium.org/p/client.v8.ports/builders/V8%20Arm%20-%20builder/...

https://build.chromium.org/p/client.v8.ports/builders/V8%20Arm%20-%20debug%20...

There are a bunch of differences, but IIUC they shouldn't matter at runtime as
we auto-detect all of those:
    In GN, but not in gyp:
      -DCAN_USE_NEON

    In gyp, but not in GN:
      -mfpu=vfpv3

    In GN, but not in gyp:
      -march=armv7-a
      -mfpu=neon
      -mthumb
      -mtune=generic-armv7-a

It now also uses clang as target compiler, which confused me at first, but the
resulting executables look alright:
readelf -h d8
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0x4ccf5
  Start of program headers:          52 (bytes into file)
  Start of section headers:          11254888 (bytes into file)
  Flags:                             0x5000400, Version5 EABI, hard-float ABI

There are unfortunately no trybots. Manual swarming job is pending:
https://chromium-swarm.appspot.com/user/task/31375eb66c54d510

[jochen (gone - plz use gerrit), 2016-09-12 14:39:03]

lgtm

[Michael Achenbach, 2016-09-13 06:35:00]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2016-09-13 06:35:02]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-13 06:36:43]

Description was changed from

==========
[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true
==========

to

==========
[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true
==========

[commit-bot: I haz the power, 2016-09-13 06:36:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-13 06:37:43]

Description was changed from

==========
[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true
==========

to

==========
[gn] Switch arm cross-compile bots to gn

BUG=chromium:474921
NOTRY=true

Committed: https://crrev.com/9f42d6c2c021a772362f8db26cb705c672a38a7b
Cr-Commit-Position: refs/heads/master@{#39367}
==========

[commit-bot: I haz the power, 2016-09-13 06:37:44]

Patchset 1 (id:??) landed as
https://crrev.com/9f42d6c2c021a772362f8db26cb705c672a38a7b
Cr-Commit-Position: refs/heads/master@{#39367}