Revert of Implement arflags in the GN build.

Revert of Implement arflags in the GN build. (patchset #2 id:20001 of https://codereview.chromium.org/1909163002/ )

Reason for revert:
speculatively reverting: issues with linking on the gpu bots again: https://build.chromium.org/p/chromium.gpu/builders/Android%20Debug%20%28Nexus%206%29/builds/8079

Original issue's description:
> Implement arflags in the GN build.
>
> This flag was recently added in GN. This patch hooks it up to the toolchains
> and moves some flags to use it that previously had to be hardcoded on the
> tool command itself.
>
> Remove concurrent_links variable from gcc_toolchain which was unused.
>
> BUG=598599
> Reland of http://crrev.com/1896163003 with fix.

TBR=brucedawson@chromium.org,brettw@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=598599
Committed: https://crrev.com/2ce39e29422675764e94de94458ce3bb22fe53d3
Cr-Commit-Position: refs/heads/master@{#389000}

[jbudorick, 2016-04-22 02:16:51]

Created Revert of Implement arflags in the GN build.

[commit-bot: I haz the power, 2016-04-22 02:17:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1910393002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1910393002/1

[commit-bot: I haz the power, 2016-04-22 02:17:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-22 19:43:23]

Description was changed from

==========
Revert of Implement arflags in the GN build. (patchset #2 id:20001 of
https://codereview.chromium.org/1909163002/ )

Reason for revert:
speculatively reverting: issues with linking on the gpu bots again:
https://build.chromium.org/p/chromium.gpu/builders/Android%20Debug%20%28Nexus...

Original issue's description:
> Implement arflags in the GN build.
> 
> This flag was recently added in GN. This patch hooks it up to the toolchains
> and moves some flags to use it that previously had to be hardcoded on the
> tool command itself.
> 
> Remove concurrent_links variable from gcc_toolchain which was unused.
> 
> BUG=598599
> Reland of http://crrev.com/1896163003 with fix.

TBR=brucedawson@chromium.org,brettw@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=598599
==========

to

==========
Revert of Implement arflags in the GN build. (patchset #2 id:20001 of
https://codereview.chromium.org/1909163002/ )

Reason for revert:
speculatively reverting: issues with linking on the gpu bots again:
https://build.chromium.org/p/chromium.gpu/builders/Android%20Debug%20%28Nexus...

Original issue's description:
> Implement arflags in the GN build.
>
> This flag was recently added in GN. This patch hooks it up to the toolchains
> and moves some flags to use it that previously had to be hardcoded on the
> tool command itself.
>
> Remove concurrent_links variable from gcc_toolchain which was unused.
>
> BUG=598599
> Reland of http://crrev.com/1896163003 with fix.

TBR=brucedawson@chromium.org,brettw@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=598599

Committed: https://crrev.com/2ce39e29422675764e94de94458ce3bb22fe53d3
Cr-Commit-Position: refs/heads/master@{#389000}
==========

[commit-bot: I haz the power, 2016-04-22 19:43:24]

Patchset 1 (id:??) landed as
https://crrev.com/2ce39e29422675764e94de94458ce3bb22fe53d3
Cr-Commit-Position: refs/heads/master@{#389000}