win gn: Use /safeseh, not /SAFESEH

build/config/win/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 
 assert(is_win)
 
 # This is included by reference in the //build/config/compiler config that
 # is applied to all targets. It is here to separate out the logic that is
 # Windows-only.
 config("compiler") {
   asmflags = [
-    # When /SAFESEH is specified, the linker will only produce an image if it
+    # When /safeseh is specified, the linker will only produce an image if it
     # can also produce a table of the image's safe exception handlers. This
     # table specifies for the operating system which exception handlers are
-    # valid for the image.
-    "/SAFESEH",
+    # valid for the image. Note that /SAFESEH isn't accepted on the command
+    # line, only /safeseh.
+    "/safeseh",
   ]
 
   cflags = [
     "/Gy",  # Enable function-level linking.
     "/GS",  # Enable buffer security checking.
     "/FS",  # Preserve previous PDB behavior.
     "/bigobj",  # Some of our files are bigger than the regular limits.
   ]
 
   # Force C/C++ mode for the given GN detected file type. This is necessary
@@ skipping 278 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }