New VS 2015 package with two hot fixes

This new VS 2015 package contains updated c2.dll, link.exe, and cl.exe
binaries (four variations of each) to fix two bugs. One is a silent
bad code-gen bug:

https://connect.microsoft.com/VisualStudio/feedback/details/2291638

The other is a bug that causes randomly corrupt object files in
debug builds:
https://connect.microsoft.com/VisualStudio/feedback/details/1853228

The modification to cl.exe is purely a change to the link timestamp so
that goma will detect that this is a new toolchain.

Local testing and testing with crrev.com/1680133003 indicate that this
is working correctly. The crrev.com/1680133003 compiles failed until
goma was updated (good) and all of the tests passed. Committing this
change will cause the VS 2015 fyi builders to start using this compiler
which will let us gather data on whether the corrupt object file bug is
fixed.

BUG=440500

Review URL: https://codereview.chromium.org/1696813002

Cr-Commit-Position: refs/heads/master@{#375221}

build/vs_toolchain.py

@@ -278,8 +278,8 @@ def _GetDesiredVsToolchainHashes():
   """Load a list of SHA1s corresponding to the toolchains that we want installed
   to build with."""
   if GetVisualStudioVersion() == '2015':
-    # Update 1 with Debuggers, UCRT installers and ucrtbased.dll
-    return ['523b6c2d3df300b2c8538cdc0beac404726af051']
+    # Update 1 with hot fixes.
+    return ['b349b3cc596d5f7e13d649532ddd7e8db39db0cb']
   else:
     # Default to VS2013.
     return ['4087e065abebdca6dbd0caca2910c6718d2ec67f']