title: Can't include generated protobuf files in cpp file
body: <p>I have a problem regarding generated protobuf files which wont include in my C++ source files.</p>
  <p>Project structure :</p>
  <pre><code>src/
  ├── Folder/
  │    ├── file1.cpp
  │    └── file2.cpp
  ├── CMakeLists.txt
  ├── Proto/
  │    ├── protofile.proto
  │    └── CMakeLists.txt
  └── Build/
  </code></pre>
  <p><code>CMakeLists.txt</code> in Proto folder:</p>
  <pre><code>INCLUDE(FindProtobuf)
  INCLUDE_DIRECTORIES(${PROTOBUF_INCLUDE_DIR})
  PROTOBUF_GENERATE_CPP(PROTO_SRC PROTO_HDRS protofile.proto)
  SET_SOURCE_FILES_PROPERTIES(PROTO_SRC PROTO_HDRS PROPERTIES GENERATED TRUE)
  add_library(protoLib ${PROTO_SRC} ${PROTO_HDRS})
  </code></pre>
  <p>In the <code>CMakeLists.txt</code> in main folder:</p>
  <pre><code>...
  add_subdirectory(Proto)
  target_link_libraries(${TARGET} PUBLIC protoLib)
  ...
  </code></pre>
  <p>The proto file generates fine to the build folder as <code>protofile.pb.cc</code> and <code>protofile.pb.h</code> but when I try to include it in <code>file1.cpp</code> it wont find it</p>
  <pre><code>#include &lt;Proto/protofile.pb.h&gt;
  ...
  </code></pre>