cmake copy wrong files to folder EXT_BUILD_DEPS

[fausturs]

I'm using the cmake tool to build my cmake project with bazel.

one of my deps is glog/0.5.0

I find rules_foreign_cc copy all .h files of glog to folder EXT_BUILD_DEPS/include.

As we can see the glog project https://github.com/google/glog/blob/v0.5.0/bazel/glog.bzl#L140-L147

we only need EXT_BUILD_DEPS/include/glog/xxx.h

But actually, we get all headers even it declare in the filed srcs, like EXT_BUILD_DEPS/include/demangle.h, it's src/demangle.h in glog, declare in https://github.com/google/glog/blob/v0.5.0/bazel/glog.bzl#L120

This caused some conflicts in our header files.

Is this behavior expected, or are there ways we can avoid unnecessary copies?