Lacros: Remove complete-member-pointers flag from lacros.

This removes cflag complete-member-pointers from lacros build to make it
consistent with ash-chrome (a.k.a chromeos-chrome).

This is in preparation to switching lacros-chrome to
target_os="chromeos" from target_os="linux". Once the switch is
completed, the !is_chromeos_lacros condition should be removed as
suggested in the comment.

Bug: 1052397
Change-Id: I4440c311407adf9e932ac32e44648c4433c6a9de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631895Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Yuta Hijikata <ythjkt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845017}

build/config/compiler/BUILD.gn

@@ -732,8 +732,10 @@ config("compiler") {
   # This flag enforces that member pointer base types are complete. It helps
   # prevent us from running into problems in the Microsoft C++ ABI (see
   # https://crbug.com/847724).
+  # TODO(crbug/1052397): Remove is_chromeos_lacros once lacros-chrome switches
+  # to target_os="chromeos".
   if (is_clang && !is_nacl && target_os != "chromeos" && !use_xcode_clang &&
-      (is_win || use_custom_libcxx)) {
+      !is_chromeos_lacros && (is_win || use_custom_libcxx)) {
     cflags += [ "-fcomplete-member-pointers" ]
   }