clang/win: Build chromium code without -Wno-incompatible-pointer-types.

third_party/iaccessible2/BUILD.gn

Index: third_party/iaccessible2/BUILD.gn
diff --git a/third_party/iaccessible2/BUILD.gn b/third_party/iaccessible2/BUILD.gn
index 6ebcee644d3d0c166e4fefc5a5a73e1de95f5892..c4203567c975f0f3cd0a61809ba023de1c881969 100644
--- a/third_party/iaccessible2/BUILD.gn
+++ b/third_party/iaccessible2/BUILD.gn
@@ -30,4 +30,11 @@ shared_library("IAccessible2Proxy") {
   deps = [
     ":iaccessible2",
   ]
+
+  config("IAccessible2Proxy_warnings") {
+    if (is_clang) {
+      cflags = [ "-Wno-incompatible-pointer-types" ]
+    }
+  }
+  configs += [ ":IAccessible2Proxy_warnings" ]
 }