💹 Update GN docs about target_cpu to encourage use of current_cpu

Update GN docs about target_cpu to encourage use of current_cpu

BUG=616819
Committed: https://crrev.com/bfdee36d31a624d330b60b481fc26d10dff81b97
Cr-Commit-Position: refs/heads/master@{#398661}

[agrieve, 2016-06-03 18:39:29]

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

[brettw, 2016-06-03 20:50:40]

lgtm

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
File tools/gn/docs/cross_compiles.md (right):

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
tools/gn/docs/cross_compiles.md:92: defines = ["CPU_IS_32_BIT"]
Style nit: spaces inside the []

[Dirk Pranke, 2016-06-04 23:03:52]

dpranke@chromium.org changed reviewers:
+ dpranke@chromium.org

[Dirk Pranke, 2016-06-04 23:03:53]

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
File tools/gn/docs/cross_compiles.md (right):

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
tools/gn/docs/cross_compiles.md:79: to use `current_cpu` rather than
`target_cpu`**.
I don't know if "almost always" is really right. Current usage looks like we use
current_cpu 3x as often as target_cpu, and I doubt that most of the target_cpu
uses are actually wrong.

So, that's definitely at least "most of the time" but maybe not "almost always".

[agrieve, 2016-06-08 17:21:48]

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
File tools/gn/docs/cross_compiles.md (right):

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
tools/gn/docs/cross_compiles.md:79: to use `current_cpu` rather than
`target_cpu`**.
On 2016/06/04 23:03:53, Dirk Pranke wrote:
> I don't know if "almost always" is really right. Current usage looks like we
use
> current_cpu 3x as often as target_cpu, and I doubt that most of the target_cpu
> uses are actually wrong.
> 
> So, that's definitely at least "most of the time" but maybe not "almost
always".
> 

Done.

https://codereview.chromium.org/2038733003/diff/1/tools/gn/docs/cross_compile...
tools/gn/docs/cross_compiles.md:92: defines = ["CPU_IS_32_BIT"]
On 2016/06/03 20:50:40, brettw wrote:
> Style nit: spaces inside the []

Done.

[agrieve, 2016-06-08 17:43:56]

https://codereview.chromium.org/2038733003/diff/20001/tools/gn/docs/cross_com...
File tools/gn/docs/cross_compiles.md (right):

https://codereview.chromium.org/2038733003/diff/20001/tools/gn/docs/cross_com...
tools/gn/docs/cross_compiles.md:98: group("fat_bundle") {
hmm, actually, I don't think this example is correct.

E.g., if target_cpu == "arm", and a target explicitly build
":fat_bundle(//build/toolchain/android:arm64)", it would do the wrong thing.

Only valid example I could find in our code was from here:
https://cs.chromium.org/chromium/src/build/config/sysroot.gni

So changed to this.

[Dirk Pranke, 2016-06-08 19:03:34]

lgtm

[agrieve, 2016-06-08 19:35:47]

The CQ bit was checked by agrieve@chromium.org

[agrieve, 2016-06-08 19:35:48]

The patchset sent to the CQ was uploaded after l-g-t-m from brettw@chromium.org
Link to the patchset: https://codereview.chromium.org/2038733003/#ps40001
(title: "change target_cpu example")

[commit-bot: I haz the power, 2016-06-08 19:36:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2038733003/40001

[commit-bot: I haz the power, 2016-06-08 20:30:30]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-06-08 20:32:47]

Description was changed from

==========
Update GN docs about target_cpu to encourage use of current_cpu

BUG=616819
==========

to

==========
Update GN docs about target_cpu to encourage use of current_cpu

BUG=616819

Committed: https://crrev.com/bfdee36d31a624d330b60b481fc26d10dff81b97
Cr-Commit-Position: refs/heads/master@{#398661}
==========

[commit-bot: I haz the power, 2016-06-08 20:32:48]

Patchset 3 (id:??) landed as
https://crrev.com/bfdee36d31a624d330b60b481fc26d10dff81b97
Cr-Commit-Position: refs/heads/master@{#398661}