Remove condition in absl_config for cflags

This CL replaces the condition `dawn_standalone` with
`!build_with_chromium` when setting cflags for the absl_source_set
build configs. This removal is necessary for ANGLE to be able to
build dawn native as it needs the "-Wno-unreachable-code-break" flag
to be set for dawn's abseil build.

Bug: angleproject:8477
Change-Id: I644d216339da60eccb34a0467b863b60e06efb0c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/174080
Commit-Queue: Liza Burakova <liza@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
diff --git a/third_party/gn/abseil-cpp/BUILD.gn b/third_party/gn/abseil-cpp/BUILD.gn
index f08f93e..4bb1c23 100644
--- a/third_party/gn/abseil-cpp/BUILD.gn
+++ b/third_party/gn/abseil-cpp/BUILD.gn
@@ -30,7 +30,7 @@
 import("${dawn_root}/scripts/dawn_features.gni")
 
 config("absl_config") {
-  if (dawn_standalone && is_clang) {
+  if (!build_with_chromium && is_clang) {
     cflags = [
       # Allow the use of enable_if()
       "-Wno-gcc-compat",