Make is_win_fastlink imply -fstandalone-debug for clang

Visual Studio can't find type information outside of the object file
currently being debugged with /DEBUG:FASTLINK. So, every object file
needs to have "standalone" debug information in this mode. However, that
generates a lot more debug info and slows down normal links, so only do
this when we know fastlink is in use.

While we're at it, explicitly pass -fno-standalone-debug to clang when
we're not using is_win_fastlink. This will make sure Chromium keeps using
limited debug info if clang switches the default for -fstandalone-debug.

R=thakis@chromium.org,brucedawson@chromium.org
BUG=657518

Review-Url: https://codereview.chromium.org/2587603002
Cr-Commit-Position: refs/heads/master@{#440163}
1 file changed