win gn: Use /safeseh, not /SAFESEH

[14421->5901/20355 ~33] ASM obj/third_party/crashpad/crashpad/util/util/capture_context.obj
MASM : warning A4018:invalid command-line option : /SAFESEH
MASM : warning A4018:invalid command-line option : /SFESEH
MASM : warning A4018:invalid command-line option : /SESEH
MASM : warning A4018:invalid command-line option : /SSEH
MASM : warning A4018:invalid command-line option : /SEH
MASM : warning A4018:invalid command-line option : /SH

BUG=546288
R=brettw@chromium.org

Review URL: https://codereview.chromium.org/1470483002

Cr-Commit-Position: refs/heads/master@{#360960}
1 file changed