Use llvm-opt's LTO pass list instead of generic O2/O3 pass list for LTO

Use llvm-opt's LTO pass list instead of generic O2/O3 pass list for LTO
This reduces pnacl's link time significantly at basically no cost in runtime*

*(I ran SPEC, and a couple of benchmarks were a bit slower, but most were the same or faster. Unfortunately we have no good way to get a better measurement other than committing and rolling DEPS) 
R=jvoung@chromium.org
BUG=

Committed: https://src.chromium.org/viewvc/native_client?view=rev&revision=11070

[jvoung - send to chromium..., 2013-03-20 16:36:23]

On 2013/03/20 01:10:48, Derek Schuff wrote:

You might have to make sure dwarf_local_var_nexe built with -O0 for LINKFLAGS
also, or make the test more robust somehow?

[Derek Schuff, 2013-03-21 20:54:51]

On 2013/03/20 16:36:23, jvoung wrote:
> On 2013/03/20 01:10:48, Derek Schuff wrote:
> 
> You might have to make sure dwarf_local_var_nexe built with -O0 for LINKFLAGS
> also, or make the test more robust somehow?
Done.

[jvoung - send to chromium..., 2013-03-21 21:17:05]

lgtm

https://codereview.chromium.org/12843006/diff/8001/pnacl/driver/pnacl-ld.py
File pnacl/driver/pnacl-ld.py (right):

https://codereview.chromium.org/12843006/diff/8001/pnacl/driver/pnacl-ld.py#n...
pnacl/driver/pnacl-ld.py:44: 'OPT_FLAGS': '${#OPT_LEVEL && !OPT_LEVEL == 0 ?
${OPT_LTO_FLAGS}} ${OPT_STRIP_%STRIP_MODE%} ' +
80 cols

[jvoung - send to chromium..., 2013-03-21 21:23:37]

https://codereview.chromium.org/12843006/diff/8001/pnacl/driver/pnacl-ld.py
File pnacl/driver/pnacl-ld.py (right):

https://codereview.chromium.org/12843006/diff/8001/pnacl/driver/pnacl-ld.py#n...
pnacl/driver/pnacl-ld.py:43: 'OPT_LTO_FLAGS': '-std-link-opts
-disable-internalize',
might also want to leave a comment on why -disable-internalize is used

[Derek Schuff, 2013-03-26 23:19:57]

Committed patchset #3 manually as r11070 (presubmit successful).