For Windows-Clang-Debug, use -fstandalone-debug to get better debug info

Without this, debug clang builds on windows have very little debug info.
Fix is based on Chromium's handling of this (they have several tactics,
depending on linker, etc...)

https://cs.chromium.org/chromium/src/build/config/compiler/BUILD.gn?l=2194

Change-Id: Ib1b3aa4cdf4e2daa762d994bea94dc3c691cf359
Reviewed-on: https://skia-review.googlesource.com/154540
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
1 file changed