Support spaces in Mac GN build output names.

Support spaces in Mac GN build output names.

We can't use object paths with spaces in them due to a mismatch between Ninja and the Mac LD's filelist parameter (explained in more detail in a comment added in the mac toolchain GN file). In order to support output_names with spaces, the object file directory must be based on something else.

Adds a new substitution "{{target_label}}" to the tool that expands to the target name after the colon, not overridden by the output_name. This makes more sense from a directory structure perspective, and label names won't have spaces (they can but don't, and with this change won't work on Mac).

Also adds quoting for Mac tool commands so spaces will work in names.

I made the change in the Mac toolchain definition for testing, but it is currently commented out pending the binary roll. After the binary roll, we should uncomment this and update the other toolchains to match.

BUG=546894
Committed: https://crrev.com/782b1bc8562e9adbb1ea7d98929d6709ff7290b9
Cr-Commit-Position: refs/heads/master@{#358792}

[brettw, 2015-11-10 00:36:14]

brettw@chromium.org changed reviewers:
+ andybons@chromium.org

[brettw, 2015-11-10 00:36:21]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-11-10 00:40:43]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1436563003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1436563003/1

[Bons, 2015-11-10 00:56:00]

lgtm

[commit-bot: I haz the power, 2015-11-10 01:56:01]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-10 01:56:01]

Dry run: This issue passed the CQ dry run.

[brettw, 2015-11-10 04:56:56]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-11-10 04:57:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1436563003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1436563003/1

[commit-bot: I haz the power, 2015-11-10 05:03:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-10 05:03:58]

Patchset 1 (id:??) landed as
https://crrev.com/782b1bc8562e9adbb1ea7d98929d6709ff7290b9
Cr-Commit-Position: refs/heads/master@{#358792}

[Dirk Pranke, 2015-11-10 20:14:47]

Correct me if I'm wrong, but ...

a) I think the CL description is actually wrong, in that you added
{{label_name}}, not {{target_label}}

b) you probably should've updated tools/gn/docs/reference.md as well

right?

[brettw, 2015-11-10 21:45:32]

Guess it's too late for CL description. I'll update reference next time I do a
GN patch.