Fix Bazel build for XNNPACK when using emscripten toolchain.

These fixes allow TF.js to depend and successfully build the XNNPACK library in the open-source world.

PiperOrigin-RevId: 273317397
diff --git a/build_defs.bzl b/build_defs.bzl
index 1e9617a..5fa075c 100644
--- a/build_defs.bzl
+++ b/build_defs.bzl
@@ -118,6 +118,7 @@
             ":optimized_build": optimized_copts,
             "//conditions:default": [],
         }),
+        includes = ["include", "src"],
         linkstatic = True,
         linkopts = select({
             ":linux_k8": ["-lpthread"],