Win/GN: Make no_exception config explicit.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 79723f6cc76c041697955f5c7de91e2935e78aa5..eb0c7bf3fdb7bb71b85dcbbf4e9357a5101ad813 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1144,6 +1144,20 @@ config("no_rtti") {
   }
 }
 
+# exceptions -------------------------------------------------------------------
+#
+# Allows turning exceptions on or off.

[brettw, 2016/08/31 17:01:20]

Can this comment be a little more precise? This will disable exceptions when
applied, which are normally enabled in C++.

+
+config("no_exceptions") {
+  if (is_posix) {
+    cflags_cc = [ "-fno-exceptions" ]
+    cflags_objcc = cflags_cc
+  }
+  if (is_win) {
+    defines = [ "_HAS_EXCEPTIONS=0" ]
+  }
+}
+
 # Warnings ---------------------------------------------------------------------
 
 # This will generate warnings when using Clang if code generates exit-time