title: Undefined symbol for custom .h and cpp using CMake
body: <p>It's been over a decade since I used C++ and this whole CMake thing is completely new to me. My question is specifically how do I configure a CMake project so that it won't get this undefined symbol error. </p>
  
  <p>The error message is below:</p>
  
  <pre><code>====================[ Build | glfw_template | Debug ]===========================
  "/Users/brianyeh/Library/Application Support/JetBrains/Toolbox/apps/CLion/ch-0/193.6911.21/CLion.app/Contents/bin/cmake/mac/bin/cmake" --build /Users/brianyeh/CLionProjects/glfw_template/cmake-build-debug --target glfw_template -- -j 4
  [ 50%] Linking CXX executable bin/glfw_template
  Undefined symbols for architecture x86_64:
    "_LoadShaders", referenced from:
        init() in main.cpp.o
  ld: symbol(s) not found for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  make[3]: *** [bin/glfw_template] Error 1
  make[2]: *** [CMakeFiles/glfw_template.dir/all] Error 2
  make[1]: *** [CMakeFiles/glfw_template.dir/rule] Error 2
  make: *** [glfw_template] Error 2
  </code></pre>
  
  <p>Please reference this link to see the project: <a href="https://github.com/crimsonalucard/glfw_template" rel="nofollow noreferrer">https://github.com/crimsonalucard/glfw_template</a></p>
  
  <p>The desired behavior is that the project compiles under CMake. </p>