Feel free to wrap it in an #ifdef [gnu], or patch it out in the ebuild. Removing it from upstream will probably break someone else's build since no one would add that line just for fun.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/3fd4ec6a4d3225378d9019b0e96468a4eda1415d

commit 3fd4ec6a4d3225378d9019b0e96468a4eda1415d
Author: Manoj Gupta <manojgupta@google.com>
Date: Thu Jul 20 23:41:22 2017

stressapptest: Force building with libstdc++.

stressapptest does not build with libc++ because of
compilation errors. Force use of libstdc++ to avoid the errors.

In file included from sat.cc:44:
In file included from ./disk_blocks.h:29:
./sattypes.h:33:17: error: expected namespace name
using namespace __gnu_cxx;  // NOLINT

BUG= chromium:747053 
TEST=stressapptest builds with libstdc++.

Change-Id: I60045a2d701a89af46706016dde0f5e7daace3de
Reviewed-on: https://chromium-review.googlesource.com/580072
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Nick Sanders <nsanders@chromium.org>

[add] https://crrev.com/3fd4ec6a4d3225378d9019b0e96468a4eda1415d/chromeos/config/env/dev-util/stressapptest

Currently forced to build with libstdc++. May revisit this in future.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/portage-stable/+/35c18a2112c9a9e481c03647c8566c4b77b9bcb1

commit 35c18a2112c9a9e481c03647c8566c4b77b9bcb1
Author: Manoj Gupta <manojgupta@google.com>
Date: Sat Sep 02 07:18:27 2017

stressapptest: Drop unused __gnu_cxx namespace from header.

Patch out unused __gnu_cxx namespace used from stressapptest.
This fixes build issues with libc++.

upstream bug: https://github.com/stressapptest/stressapptest/issues/47

BUG= chromium:747053 
TEST=stressapptest builds with/without libc++.

Change-Id: Ic894fdb74668ee0ab7d1c8920e223c1b112bd606
Reviewed-on: https://chromium-review.googlesource.com/647688
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[rename] https://crrev.com/35c18a2112c9a9e481c03647c8566c4b77b9bcb1/dev-util/stressapptest/stressapptest-1.0.8-r1.ebuild
[add] https://crrev.com/35c18a2112c9a9e481c03647c8566c4b77b9bcb1/dev-util/stressapptest/files/stressapptest-gnu_cxx-namespace.patch

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/e912424c0271d1bba893e0f3aac017fe9c3db6f4

commit e912424c0271d1bba893e0f3aac017fe9c3db6f4
Author: Manoj Gupta <manojgupta@google.com>
Date: Sat Sep 02 14:52:10 2017

stressapptest: Allow building with libc++.

stressapptest packages is already fixed to build with libc++.
Drop forced build using libstdc++.

BUG= chromium:747053 
TEST=stressapptest builds with/without libc++.

Change-Id: I74d8e572c94e26611eccbf5cf4fe0b92828e203d
Reviewed-on: https://chromium-review.googlesource.com/648475
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Manoj Gupta <manojgupta@chromium.org>

[delete] https://crrev.com/25cea766cf00fbbb7de98a1979165ead38cf0bee/chromeos/config/env/dev-util/stressapptest