Reland of Use sysroot by default for all linux builds

Reland of Use sysroot by default for all linux builds (patchset #1 id:1 of https://codereview.chromium.org/1473363002/ )

Reason for revert:
Couldn't reproduce the failure.

Original issue's description:
> Revert of Use sysroot by default for all linux builds (patchset #7 id:120001 of https://codereview.chromium.org/1464983003/ )
>
> Reason for revert:
> Seems to have caused issues with goma: https://code.google.com/p/chromium/issues/detail?id=560973
>
> Original issue's description:
> > Use sysroot by default for all linux builds
> >
> > Using a sysroot was already the default for official
> > build and when cross compiling (e.g. arm, mips, x86-32).
> > This change makes it the default in all cases.
> >
> > The old behavior of building against local
> > system libraries can still be achieved by
> > setting use_sysroot=0
> >
> > BUG=504446
> >
> > Committed: https://crrev.com/a931efd5dc8d8783ce73a64fc641627866b6869d
> > Cr-Commit-Position: refs/heads/master@{#361197}
>
> TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=504446
>
> Committed: https://crrev.com/05373dc078f0d5d3f2fb1398db9a4008a55d9016
> Cr-Commit-Position: refs/heads/master@{#361405}

TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=504446
Committed: https://crrev.com/964155752e49f75260e86ba824fcec81b3fd4c3d
Cr-Commit-Position: refs/heads/master@{#361411}

[Sam Clegg, 2015-11-24 19:24:41]

Created Reland of Use sysroot by default for all linux builds

[Sam Clegg, 2015-11-24 19:25:42]

Description was changed from

==========
Reland of Use sysroot by default for all linux builds (patchset #1 id:1 of
https://codereview.chromium.org/1473363002/ )

Reason for revert:
Relanding sysroot change

Original issue's description:
> Revert of Use sysroot by default for all linux builds (patchset #7 id:120001
of https://codereview.chromium.org/1464983003/ )
> 
> Reason for revert:
> Seems to have caused issues with goma:
https://code.google.com/p/chromium/issues/detail?id=560973
> 
> Original issue's description:
> > Use sysroot by default for all linux builds
> >
> > Using a sysroot was already the default for official
> > build and when cross compiling (e.g. arm, mips, x86-32).
> > This change makes it the default in all cases.
> >
> > The old behavior of building against local
> > system libraries can still be achieved by
> > setting use_sysroot=0
> >
> > BUG=504446
> >
> > Committed: https://crrev.com/a931efd5dc8d8783ce73a64fc641627866b6869d
> > Cr-Commit-Position: refs/heads/master@{#361197}
> 
> TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=504446
> 
> Committed: https://crrev.com/05373dc078f0d5d3f2fb1398db9a4008a55d9016
> Cr-Commit-Position: refs/heads/master@{#361405}

TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=504446
==========

to

==========
Reland of Use sysroot by default for all linux builds (patchset #1 id:1 of
https://codereview.chromium.org/1473363002/ )

Reason for revert:
Couldn't reproduce the failure.

Original issue's description:
> Revert of Use sysroot by default for all linux builds (patchset #7 id:120001
of https://codereview.chromium.org/1464983003/ )
> 
> Reason for revert:
> Seems to have caused issues with goma:
https://code.google.com/p/chromium/issues/detail?id=560973
> 
> Original issue's description:
> > Use sysroot by default for all linux builds
> >
> > Using a sysroot was already the default for official
> > build and when cross compiling (e.g. arm, mips, x86-32).
> > This change makes it the default in all cases.
> >
> > The old behavior of building against local
> > system libraries can still be achieved by
> > setting use_sysroot=0
> >
> > BUG=504446
> >
> > Committed: https://crrev.com/a931efd5dc8d8783ce73a64fc641627866b6869d
> > Cr-Commit-Position: refs/heads/master@{#361197}
> 
> TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=504446
> 
> Committed: https://crrev.com/05373dc078f0d5d3f2fb1398db9a4008a55d9016
> Cr-Commit-Position: refs/heads/master@{#361405}

TBR=dpranke@chromium.org,thestig@chromium.org,thakis@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=504446
==========

[Sam Clegg, 2015-11-24 19:26:24]

The CQ bit was checked by sbc@chromium.org

[commit-bot: I haz the power, 2015-11-24 19:27:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1472873004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1472873004/1

[commit-bot: I haz the power, 2015-11-24 19:29:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-24 19:30:51]

Patchset 1 (id:??) landed as
https://crrev.com/964155752e49f75260e86ba824fcec81b3fd4c3d
Cr-Commit-Position: refs/heads/master@{#361411}