add emscripten compiler config_setting
diff --git a/cc/compiler/BUILD b/cc/compiler/BUILD
index 41f00e4..4503aa8 100644
--- a/cc/compiler/BUILD
+++ b/cc/compiler/BUILD
@@ -69,3 +69,8 @@
     name = "msvc-cl",
     flag_values = {"@bazel_tools//tools/cpp:compiler": "msvc-cl"},
 )
+
+config_setting(
+    name = "emscripten",
+    flag_values = {"@bazel_tools//tools/cpp:compiler": "emscripten"},
+)