Fix diagnostic suppression when MSVC is used.

They don't work when MSVC is used:
https://ci.chromium.org/p/webrtc/builders/try/win_x64_msvc_dbg/20933?

Bug: None
Change-Id: I9a97f385bbfff53c616e0ff38d5a1784bddd7c01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2274505Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#783935}

third_party/abseil-cpp/absl/container/BUILD.gn

@@ -351,7 +351,11 @@ absl_source_set("btree") {
 absl_source_set("inlined_vector_test") {
   testonly = true
   sources = [ "inlined_vector_test.cc" ]
-  cflags_cc = [ "-Wno-deprecated-declarations" ]
+  if (is_win && !is_clang) {
+    cflags_cc = [ "/wd4996" ]
+  } else {
+    cflags_cc = [ "-Wno-deprecated-declarations" ]
+  }
   deps = [
     ":counting_allocator",
     ":inlined_vector",

third_party/abseil-cpp/absl/meta/BUILD.gn

@@ -12,7 +12,9 @@ absl_source_set("type_traits") {
 absl_source_set("type_traits_test") {
   testonly = true
   sources = [ "type_traits_test.cc" ]
-  cflags_cc = [ "-Wno-unused-private-field" ]
+  if (is_clang) {
+    cflags_cc = [ "-Wno-unused-private-field" ]
+  }
   deps = [
     ":type_traits",
     "//third_party/googletest:gtest",

third_party/abseil-cpp/absl/types/BUILD.gn

@@ -117,7 +117,9 @@ absl_source_set("compare") {
 # absl_source_set("variant_test") {
 #   testonly = true
 #   sources = [ "variant_test.cc" ]
-#   cflags_cc = [ "-Wno-unused-function" ]
+#   if (is_clang) {
+#     cflags_cc = [ "-Wno-unused-function" ]
+#   }
 #   deps = [
 #     ":variant",
 #     "//third_party/abseil-cpp/absl/base:config",