Update static_initializers tool to detect clang's initializers

Clang currently puts the undecorated symbol name in the debug info for
initializer functions. Fixing that is not simply a matter of calling
UnDecorateSymbolName in Clang because we want our output to be the same
when we're cross-compiling, and we don't have our own MS ABI demangler.
Do the undecoration in this tool in the meantime.

R=brucedawson@chromium.org

Bug: 777943
Change-Id: I3087e4fdbde849762d446ffcc9aa2ea60e9cb21e
Reviewed-on: https://chromium-review.googlesource.com/752187
Commit-Queue: Reid Kleckner <rnk@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#514373}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b711f2361e5bfd3a42bf7f382eb24779383285af
2 files changed