title: Cocoapods header conflict between libopus and abseil
body: <p>I have an Xcode project with the following Podfile :</p>
  <pre><code>pod '!ProtoCompiler-gRPCPlugin', '~&gt; 1.33'
  pod 'gRPC', '~&gt; 1.33'
  pod 'libopus'
  </code></pre>
  <p>The issue is that since GRPC decide to use Abseil as a dependency, a weird conflict is happening.
  When compiling, I get the following error on Pods/abseil/base/config.h:</p>
  <p><code>'absl/base/options.h' file not found</code></p>
  <p>but the previous call in the stack is actually located in Pods/libopus/float/warped_autocorrelation_FLP.c :</p>
  <p><code>#include &quot;config.h&quot;</code></p>
  <p>This doesn't make sense as the specific <code>config.h</code> libopus is trying to get is actually in the same pod directory.</p>
  <p>Any idea how to fix this? I tried multiple versions of libopus, but the static version is causing issues of its own.</p>