use absolute path to clang plugins

use absolute path to clang plugins

clang + icecc has problems finding libFindBadConstructs.so, probably
due to a path bug in icecc.

We can however workaround this bug by using the canonical absolute path
instead of an absolute path that includes redundant directories (ie
remove "tools/clang/scripts/../../../" from the middle).  This has the
benefit of simplifying and shortening clang compile commands.

BUG=409571
Committed: https://crrev.com/e98080bad4592b495158eaaf2bc10f03b6ead511
Cr-Commit-Position: refs/heads/master@{#295446}

[rune, 2014-09-01 09:39:15]

I needed to modify blink_gc_plugin_flags.sh too when compiling content_shell.

[Mostyn Bramley-Moore, 2014-09-01 09:47:00]

On 2014/09/01 09:39:15, rune wrote:
> I needed to modify blink_gc_plugin_flags.sh too when compiling content_shell.

Added in patchset 2.

[Mostyn Bramley-Moore, 2014-09-01 10:07:18]

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

[Mostyn Bramley-Moore, 2014-09-01 10:08:16]

@Nico: PTAL, this allows us to use clang with icecc, without having to disable
the plugins.

[Nico, 2014-09-01 19:22:50]

Did you file a bug with icecc?

[Mostyn Bramley-Moore, 2014-09-01 19:37:34]

On 2014/09/01 19:22:50, Nico (hiding) wrote:
> Did you file a bug with icecc?

We haven't yet, but I will once I have time.  I think this patch is worthwhile
regardless, since it simplifies our build commands.

[Nico, 2014-09-01 19:39:28]

On 2014/09/01 19:37:34, Mostyn Bramley-Moore wrote:
> On 2014/09/01 19:22:50, Nico (hiding) wrote:
> > Did you file a bug with icecc?
> 
> We haven't yet, but I will once I have time.  I think this patch is worthwhile
> regardless, since it simplifies our build commands.

It also makes generated ninja files and command lines a bit longer.

[Mostyn Bramley-Moore, 2014-09-01 19:50:22]

> It also makes generated ninja files and command lines a bit longer.

Actually I think it makes the command lines shorter- without this patch the
command lines have this (for example):
/home/mostyn/code/opera/work/chromium/src/tools/clang/scripts/../../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so

And with this patch:
/home/mostyn/code/opera/work/chromium/src/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so

[Nico, 2014-09-01 23:44:40]

Oh, I see. Then the CL description is wrong, as the prior path is also absolute
(?)

[Mostyn Bramley-Moore, 2014-09-02 06:24:47]

On 2014/09/01 23:44:40, Nico (hiding) wrote:
> Oh, I see. Then the CL description is wrong, as the prior path is also
absolute
> (?)

The description didn't say that that the current path is relative, but I can see
how it might be easy to misunderstand.  

I have tried to clarify this a bit in the description now (it's hard to find a
good/concise way to describe absolute paths that contain "..").

[Mostyn Bramley-Moore, 2014-09-04 07:29:18]

> I have tried to clarify this a bit in the description now (it's hard to find a
> good/concise way to describe absolute paths that contain "..").

Or perhaps it would be better to say something like:
"Remove superfluous 'tools/clang/scripts/../../../' from the path to
libFindBadConstructs.so" ?

[Mostyn Bramley-Moore, 2014-09-17 23:30:51]

*ping*

[Nico, 2014-09-18 01:47:29]

lgtm

(sorry, I thought I already had lg'd)

Please do file an icecc bug though.

[Mostyn Bramley-Moore, 2014-09-18 07:28:36]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2014-09-18 07:28:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/525733005/20001

[commit-bot: I haz the power, 2014-09-18 07:31:32]

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

[commit-bot: I haz the power, 2014-09-18 07:31:33]

Try jobs failed on following builders:
  mac_gpu on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/mac_gpu/builds/57569)
  mac_chromium_compile_dbg on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[Mostyn Bramley-Moore, 2014-09-18 08:28:31]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2014-09-18 08:29:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/525733005/40001

[commit-bot: I haz the power, 2014-09-18 08:39:46]

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

[commit-bot: I haz the power, 2014-09-18 08:39:46]

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

[Mostyn Bramley-Moore, 2014-09-18 08:46:38]

The CQ bit was checked by mostynb@opera.com

[commit-bot: I haz the power, 2014-09-18 08:47:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/525733005/60001

[commit-bot: I haz the power, 2014-09-18 10:14:46]

Committed patchset #4 (id:60001) as 8aa34a241d45f977a6cc6702fd9dec608e159d71

[commit-bot: I haz the power, 2014-09-18 10:56:16]

Patchset 4 (id:??) landed as
https://crrev.com/e98080bad4592b495158eaaf2bc10f03b6ead511
Cr-Commit-Position: refs/heads/master@{#295446}