I reproduced the specific issue and fixed it in r299035. I doubt that's all it will take for this bot to cycle green, so let's leave it open and see if it has any more PDB problems.

[97/57114] LINK dump_syms.exe dump_syms.exe.pdb
FAILED: dump_syms.exe dump_syms.exe.pdb 
cmd /c C:/b/depot_tools/python276_bin/python.exe ../../build/toolchain/win/tool_wrapper.py delete-file ./dump_syms.exe.pdb && C:/b/depot_tools/python276_bin/python.exe ../../build/toolchain/win/tool_wrapper.py link-wrapper environment.x86 False ../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo /OUT:./dump_syms.exe /PDB:./dump_syms.exe.pdb @./dump_syms.exe.rsp
Program aborted due to an unhandled Error:

Multiple errors:

CodeView Error: The CodeView record is corrupted.  



CodeView Error: The CodeView record is corrupted.  


from https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FCrWinClangLLD%2F5401%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout / https://build.chromium.org/p/chromium.fyi/builders/CrWinClangLLD/builds/5401

I noticed that this is affecting the non-dbg builders. Let's run those on symbol_level=0 for now while the PDB writing code gets more robust. CrWinClngLLDdbg will give us coverage of the PDB writing code in the mean time.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/95990d668523353e2a4adabff2eeccf207f1f04d

commit 95990d668523353e2a4adabff2eeccf207f1f04d
Author: rnk <rnk@chromium.org>
Date: Thu Mar 30 21:31:06 2017

Change symbol_level for ToT LLD bots

With this change, the release bots use symbol_level=0, which means they
don't make PDBs. The debug bots now make full PDBs, which exercises
LLD's PDB writing functionality more completely. They'll be red for the
foreseeable future, but it gives us something to work towards fixing.

R=thakis@chromium.org
BUG= 706492 

Review-Url: https://codereview.chromium.org/2786113003
Cr-Commit-Position: refs/heads/master@{#460886}

[modify] https://crrev.com/95990d668523353e2a4adabff2eeccf207f1f04d/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/96c9dd773e020fea6294fc80bad1bcccb7deb05d

commit 96c9dd773e020fea6294fc80bad1bcccb7deb05d
Author: rnk <rnk@chromium.org>
Date: Fri Mar 31 17:37:06 2017

Really disable symbols on the ToT Windows LLD bots

The default symbol_level on Windows is 2, not 0, so these bots are still
red because they are trying to produce PDBs.

TBR=thakis@chromium.org
BUG= 706492 
NOTRY=true

Review-Url: https://codereview.chromium.org/2788083003
Cr-Commit-Position: refs/heads/master@{#461163}

[modify] https://crrev.com/96c9dd773e020fea6294fc80bad1bcccb7deb05d/tools/mb/mb_config.pyl

https://reviews.llvm.org/D31629 should help the PDB-producing bots get farther, but who knows what will happen on larger PDBs.

The debug LLD bots are getting farther and they are making PDBs now, but now the link steps are timing out. We might want to downgrade the dbg bots back down to symbol_level=1 to make the link steps faster while we focus on filling in the rest of the PDB, and then we'll come back and optimize it.

Sounds fine, but the timeout is 2h without output or something like that. So if a link times out, maybe it's an infinite loop instead of unoptimized code somewhere.

Is this fixed now?

The bot has been looking happy lately: https://build.chromium.org/p/chromium.fyi/builders/CrWinClngLLDdbg/builds/6791

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/edcc2158fce0f0d8bdb9992186ce4c613810a652

commit edcc2158fce0f0d8bdb9992186ce4c613810a652
Author: Reid Kleckner <rnk@google.com>
Date: Fri Nov 10 00:39:47 2017

Use symbol_level=1 on non-debug LLD bots

We needed symbol_level=0 as a workaround for  http://crbug.com/706492 ,
but that's fixed upstream, so we don't need it anymore. Most bots used
symbol_level=1, so the LLD release bots should too.

R=dpranke@chromium.org, hans@chromium.org

Bug:  706492 ,  782784 
Change-Id: Idc8596df997a77e278cea82745430adc4eb25644
Reviewed-on: https://chromium-review.googlesource.com/758702
Reviewed-by: Hans Wennborg <hans@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Reid Kleckner <rnk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515371}
[modify] https://crrev.com/edcc2158fce0f0d8bdb9992186ce4c613810a652/tools/mb/mb_config.pyl