Modify the gcc_toolchain definitions in GN for NaCl compatibility

Modify the gcc_toolchain definitions in GN for NaCl compatibility.

This CL adds a number of optional settings to GN's
gcc_toolchain() template so that NaCl can use it to
define toolchains, most importantly by adding the ability
to customize post-link steps and set the default
output extensions for executables.

R=brettw@chromium.org, ncbray@chromium.org, mcgrathr@chromium.org
BUG=433528
Committed: https://crrev.com/caf3cee6fd23ffe493fe69ba08d3bd1f7d646334
Cr-Commit-Position: refs/heads/master@{#346262}

[Dirk Pranke, 2015-08-28 02:14:18]

Patchset #1 (id:1) has been deleted

[Dirk Pranke, 2015-08-28 02:14:25]

Patchset #1 (id:20001) has been deleted

[Dirk Pranke, 2015-08-28 02:19:04]

dpranke@chromium.org changed reviewers:
+ brettw@chromium.org, mcgrathr@chromium.org, ncbray@chromium.org

[Dirk Pranke, 2015-08-28 02:21:03]

Note that this patchset depends on the cleanup in
https://codereview.chromium.org/1314163005/ landing first.

This patch should have no functional effect, but it makes it clearer what
changes to the chromium toolchains were needed for NaCl to be able to use them,
and it means that the follow-on patch to switch toolchains is small and
straightforward.

[brettw, 2015-08-28 17:50:20]

lgtm

[Roland McGrath, 2015-08-28 19:59:38]

LGTM with some comment fixes.

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
File build/toolchain/gcc_toolchain.gni (right):

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
build/toolchain/gcc_toolchain.gni:39: #      command.
This sounds like it's for arguments to be added to the end of the existing link
command.  In fact, it's a second shell command that will be run after the shell
command for linking, with &&.  Make it clear.

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
build/toolchain/gcc_toolchain.gni:53: #      Whether to forceably enable or
disable component builds for this
"forcibly"

[Dirk Pranke, 2015-08-28 20:05:33]

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
File build/toolchain/gcc_toolchain.gni (right):

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
build/toolchain/gcc_toolchain.gni:39: #      command.
On 2015/08/28 19:59:37, Roland McGrath wrote:
> This sounds like it's for arguments to be added to the end of the existing
link
> command.  In fact, it's a second shell command that will be run after the
shell
> command for linking, with &&.  Make it clear.

That makes sense. I will fix it.

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
build/toolchain/gcc_toolchain.gni:53: #      Whether to forceably enable or
disable component builds for this
On 2015/08/28 19:59:37, Roland McGrath wrote:
> "forcibly"

Acknowledged.

[Dirk Pranke, 2015-08-28 20:45:30]

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
File build/toolchain/gcc_toolchain.gni (right):

https://codereview.chromium.org/1322523008/diff/40001/build/toolchain/gcc_too...
build/toolchain/gcc_toolchain.gni:42: #      command.
turns out post_solink isn't actually implemented or referenced anywhere, so I
will delete the comment.

[Dirk Pranke, 2015-08-28 22:21:20]

The CQ bit was checked by dpranke@chromium.org

[Dirk Pranke, 2015-08-28 22:21:20]

The patchset sent to the CQ was uploaded after l-g-t-m from brettw@chromium.org,
mcgrathr@chromium.org
Link to the patchset: https://codereview.chromium.org/1322523008/#ps60001
(title: "update w/ review comments, remove post_solink reference")

[commit-bot: I haz the power, 2015-08-28 22:22:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1322523008/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1322523008/60001

[commit-bot: I haz the power, 2015-08-28 23:06:15]

Committed patchset #2 (id:60001)

[commit-bot: I haz the power, 2015-08-28 23:06:55]

Patchset 2 (id:??) landed as
https://crrev.com/caf3cee6fd23ffe493fe69ba08d3bd1f7d646334
Cr-Commit-Position: refs/heads/master@{#346262}