GN: Make NaCl toolchains run on Windows host

GN: Make NaCl toolchains run on Windows host

The toolchain executables have the ".exe" suffix on Windows.  Plumb
through the readelf, nm, and strip tools for NaCl toolchains.  These
were accidentally using default host tools, which happen to work on
other host platforms, but don't exist on Windows.

BUG=512869
R=dpranke@chromium.org

Committed: https://crrev.com/34fa90d65772e8b432d5c37cd607ed6d6dcc5ca0
Cr-Commit-Position: refs/heads/master@{#359715}

[Dirk Pranke, 2015-11-13 23:34:01]

lgtm

[Roland McGrath, 2015-11-13 23:37:34]

The CQ bit was checked by mcgrathr@chromium.org

[commit-bot: I haz the power, 2015-11-13 23:38:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1447533005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1447533005/1

[commit-bot: I haz the power, 2015-11-14 01:17:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-14 01:18:04]

Patchset 1 (id:??) landed as
https://crrev.com/34fa90d65772e8b432d5c37cd607ed6d6dcc5ca0
Cr-Commit-Position: refs/heads/master@{#359715}