Fix script and compiler invocation when using non-default toolchain.

Fix script and compiler invocation when using non-default toolchain.

According to "gn help root_build_dir" the variable corresponds to the
current directory when executing all compilers and scripts. So when
building the command-line for compilers or scripts, "rebase_path"
must use "root_build_dir" instead of "root_out_dir" otherwise they
will break if building for non-default toolchain.

BUG=603180
Committed: https://crrev.com/9b9b27be5e7007fb73ef6e0087e452227d92bbc6
Cr-Commit-Position: refs/heads/master@{#402825}

[sdefresne, 2016-06-29 13:17:43]

sdefresne@chromium.org changed reviewers:
+ rsesek@chromium.org

[sdefresne, 2016-06-29 13:17:50]

Please take a look and send to CQ if LGTY.

[Robert Sesek, 2016-06-29 15:29:14]

The CQ bit was checked by rsesek@chromium.org

[Robert Sesek, 2016-06-29 15:29:15]

lgtm

[commit-bot: I haz the power, 2016-06-29 15:29:45]

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, 2016-06-29 16:03:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-29 16:05:08]

Description was changed from

==========
Fix script and compiler invocation when using non-default toolchain.

According to "gn help root_build_dir" the variable corresponds to the
current directory when executing all compilers and scripts. So when
building the command-line for compilers or scripts, "rebase_path"
must use "root_build_dir" instead of "root_out_dir" otherwise they
will break if building for non-default toolchain.

BUG=603180
==========

to

==========
Fix script and compiler invocation when using non-default toolchain.

According to "gn help root_build_dir" the variable corresponds to the
current directory when executing all compilers and scripts. So when
building the command-line for compilers or scripts, "rebase_path"
must use "root_build_dir" instead of "root_out_dir" otherwise they
will break if building for non-default toolchain.

BUG=603180

Committed: https://crrev.com/9b9b27be5e7007fb73ef6e0087e452227d92bbc6
Cr-Commit-Position: refs/heads/master@{#402825}
==========

[commit-bot: I haz the power, 2016-06-29 16:05:10]

Patchset 1 (id:??) landed as
https://crrev.com/9b9b27be5e7007fb73ef6e0087e452227d92bbc6
Cr-Commit-Position: refs/heads/master@{#402825}