Do not build stun_prober within Chrome on gn.

stun_prober does not compile on win.
https://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/79068/steps/compile%20%28with%20patch%29/logs/stdio

TBR=pthatcher@webrtc.org
BUG=

Review URL: https://codereview.webrtc.org/2303783002 .

Cr-Commit-Position: refs/heads/master@{#14024}

webrtc/p2p/BUILD.gn

@@ -163,21 +163,25 @@ source_set("libstunprober") {
   ]
 }
 
-executable("stun_prober") {
-  sources = [
-    "stunprober/main.cc",
-  ]
+if (!build_with_chromium) {
+  # Doesn't build within Chrome on Win.
 
-  configs += [ "..:common_config" ]
-  if (!build_with_chromium && is_clang) {
-    # Suppress warnings from Chrome's Clang plugins.
-    # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
-    configs -= [ "//build/config/clang:find_bad_constructs" ]
+  executable("stun_prober") {
+    sources = [
+      "stunprober/main.cc",
+    ]
+
+    configs += [ "..:common_config" ]
+    if (!build_with_chromium && is_clang) {
+      # Suppress warnings from Chrome's Clang plugins.
+      # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
+      configs -= [ "//build/config/clang:find_bad_constructs" ]
+    }
+
+    deps = [
+      ":libstunprober",
+      ":rtc_p2p",
+      "../system_wrappers:field_trial_default",
+    ]
   }
-
-  deps = [
-    ":libstunprober",
-    ":rtc_p2p",
-    "../system_wrappers:field_trial_default",
-  ]
 }