add ccache support to gn builds

add ccache support to gn builds

This can be used to inject icecc also, via the CCACHE_PREFIX environment
variable.

BUG=394501
Committed: https://crrev.com/50ff7a9494412cdab84c472db73d1e148fcec761
Cr-Commit-Position: refs/heads/master@{#305912}

[Mostyn Bramley-Moore, 2014-11-26 14:47:25]

mostynb@opera.com changed reviewers:
+ dpranke@chromium.org, thakis@chromium.org

[Mostyn Bramley-Moore, 2014-11-26 15:09:07]

mostynb@opera.com changed reviewers:
+ brettw@chromium.org

[Mostyn Bramley-Moore, 2014-11-26 16:21:52]

Brett, Dirk, Nico: please take a look- I don't have access to goma so I can't
directly confirm that I haven't broken goma builds.

There was lots of interest in this sort of patch from external contributors at
blinkon3...

Would you prefer a more generic compiler wrapper option than use_goma,
use_icecc, use_thenextgreatthing etc?  FWIW I think icecc can be handled by
use_ccache so we probably don't need another setting for that.

[Nico, 2014-11-26 17:01:06]

Brett can probably answer your question best. I think this looks good as is
(with the understanding that it's up to the folks who use this setting to
maintain it, we won't break it willfully but we might break it, yadda yadda).

Thanks!

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.gni
File build/toolchain/ccache.gni (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.g...
build/toolchain/ccache.gni:10: # clang plugins.
Is there a bug filed with ccache for this?

[brettw, 2014-11-26 21:18:14]

lgtm

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/android/...
File build/toolchain/android/BUILD.gn (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/android/...
build/toolchain/android/BUILD.gn:40: compiler_prefix = "$goma_dir/gomacc "
Maybe here we should
assert(!use_ccache, "Goma and ccache can't be used together.");\

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.gni
File build/toolchain/ccache.gni (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.g...
build/toolchain/ccache.gni:5: # Defines the configuration of ccache.
Can you mention here what ccache is?

[Mostyn Bramley-Moore, 2014-11-26 22:09:52]

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/android/...
File build/toolchain/android/BUILD.gn (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/android/...
build/toolchain/android/BUILD.gn:40: compiler_prefix = "$goma_dir/gomacc "
On 2014/11/26 21:18:14, brettw wrote:
> Maybe here we should
> assert(!use_ccache, "Goma and ccache can't be used together.");\

Done (and in the linux version also).

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.gni
File build/toolchain/ccache.gni (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.g...
build/toolchain/ccache.gni:5: # Defines the configuration of ccache.
On 2014/11/26 21:18:14, brettw wrote:
> Can you mention here what ccache is?

Done.

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.g...
build/toolchain/ccache.gni:10: # clang plugins.
On 2014/11/26 17:01:06, Nico wrote:
> Is there a bug filed with ccache for this?

ccache 3.1.10 onwards supports the -Xclang flag:
https://ccache.samba.org/releasenotes.html#_ccache_3_1_10

Though I've been trying to reproduce my earlier issue on 3.1.9 without luck. 
I'll poke around some more and adjust this comment.

[Mostyn Bramley-Moore, 2014-11-26 22:23:25]

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.gni
File build/toolchain/ccache.gni (right):

https://codereview.chromium.org/742953007/diff/80001/build/toolchain/ccache.g...
build/toolchain/ccache.gni:10: # clang plugins.
> Though I've been trying to reproduce my earlier issue on 3.1.9 without luck. 
> I'll poke around some more and adjust this comment.

(Turns out I didn't remove the new ccache from my PATH in my test script.)

[Mostyn Bramley-Moore, 2014-11-26 22:23:33]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2014-11-26 22:24:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/742953007/140001

[commit-bot: I haz the power, 2014-11-26 22:29:26]

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

[commit-bot: I haz the power, 2014-11-26 22:29:27]

Try jobs failed on following builders:
  linux_chromium_gn_dbg on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Mostyn Bramley-Moore, 2014-11-26 22:33:33]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2014-11-26 22:34:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/742953007/160001

[commit-bot: I haz the power, 2014-11-26 23:24:28]

Committed patchset #9 (id:160001)

[commit-bot: I haz the power, 2014-11-26 23:24:59]

Patchset 9 (id:??) landed as
https://crrev.com/50ff7a9494412cdab84c472db73d1e148fcec761
Cr-Commit-Position: refs/heads/master@{#305912}