title: NDK build issue: aarch64-linux-android-ar.exe xxx.cpp.o: No such file or directory
body: <p>Background: I'm building a gradle project with linked C++ project (external native build).</p>
  
  <p>In that procedure, an unexpected error happened: </p>
  
  <blockquote>
    <p>D:\jenkins_node\workspace\new_build_android2\new_android_build_test\android-ndk-r20\toolchains\llvm\prebuilt\windows-x86_64\bin\aarch64-linux-android-ar.exe: sandbox/3rd/Bullet/src/BulletCollision/CMakeFiles/BulletCollision.dir/CollisionDispatch/btActivatingCollisionAlgorithm.cpp.o: No such file or directory</p>
  </blockquote>
  
  <p>Then I reproduced this error in command line on the same machine:</p>
  
  <pre><code>D:\jenkins_node\workspace\new_build_android2\new_android_build_test\engine\projects\android\.externalNativeBuild\cmake\release\arm64-v8a&gt;D:\jenkins_node\workspace\new_build_android2\new_android_build_test\android-ndk-r20\toolchains\llvm\prebuilt\windows-x86_64\bin\aarch64-linux-android-ar.exe qc .\sandbox\3rd\Bullet\src\BulletCollision\libBulletCollision.a  @CMakeFiles/BulletCollision.rsp
  </code></pre>
  
  <p>The content of <code>@CMakeFiles/BulletCollision.rsp</code> is <a href="https://gist.github.com/zwcloud/4897dde48194e5324c899f17a3356be6" rel="nofollow noreferrer">https://gist.github.com/zwcloud/4897dde48194e5324c899f17a3356be6</a> , which contains:</p>
  
  <pre><code>sandbox/3rd/Bullet/src/BulletCollision/CMakeFiles/BulletCollision.dir/CollisionDispatch/btActivatingCollisionAlgorithm.cpp.o
  </code></pre>
  
  <p>The file <code>btActivatingCollisionAlgorithm.cpp.o</code> does exist:</p>
  
  <p><a href="https://i.stack.imgur.com/tjKSU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tjKSU.png" alt="file &lt;code&gt;btActivatingCollisionAlgorithm.cpp.o&lt;/code&gt; does exist"></a></p>
  
  <p>What's the possible reason why <code>aarch64-linux-android-ar.exe</code> reports the error that <code>btActivatingCollisionAlgorithm.cpp.o</code> doesn't exist? And how to fix this?</p>
  
  <p>UPDATE:</p>
  
  <p>I just tried </p>
  
  <pre><code>D:\jenkins_node\workspace\new_build_android2\new_android_build_test\android-ndk-r20\toolchains\llvm\prebuilt\windows-x86_64\bin\aarch64-linux-android-ar.exe qc sandbox\3rd\Bullet\src\BulletCollision\libBulletCollision.a sandbox/3rd/Bullet/src/BulletCollision/CMakeFiles/BulletCollision.dir/CollisionDispatch/btActivatingCollisionAlgorithm.cpp.o
  </code></pre>
  
  <p>And it still reported the same error:</p>
  
  <blockquote>
    <p>D:\jenkins_node\workspace\new_build_android2\new_android_build_test\android-ndk-r20\toolchains\llvm\prebuilt\windows-x86_64\bin\aarch64-linux-android-ar.exe: sandbox/3rd/Bullet/src/BulletCollision/CMakeFiles/BulletCollision.dir/CollisionDispatch/btActivatingCollisionAlgorithm.cpp.o: No such file or directory</p>
  </blockquote>
  
  <p>Environment: Win10, CMake 3.10 (downloaded by Android Studio 3.5 in Settings -> SDK Tools), Android NDK r20</p>