title: Configuring Qt 5.9.5 on Ubuntu 16.04
body: <p>I recently started working with Qt. I was trying some simple widgets. It was working as intended with no errors and suddenly Qt doesn't work anymore. I did not change any configuration/settings. I restarted my computer and I started to get the following error. I have no idea how to fix them.</p>
  
  <p>Error (when trying to open an already existing project):</p>
  
  <pre>
  /Qt/5.9.5/gcc_64/mkspecs/features/qmake_use.prf(6): 'take_first' is not a recognized replace function.
  Project ERROR: Library '' is not defined.
  Warnings while parsing QML type information of Qt/5.9.5/gcc_64/qml:
  /Qt/5.9.5/gcc_64/qml/builtins.qmltypes:1:24: Reading only version 1.1 parts.
  /Qt/5.9.5/gcc_64/qml/builtins.qmltypes:10:5: Expected only Component and ModuleApi object definitions.
  /Qt/5.9.5/gcc_64/mkspecs/features/qmake_use.prf(6): 'take_first' is not a recognized replace function.
  Project ERROR: Library '' is not defined.
  /Qt/5.9.5/gcc_64/mkspecs/features/toolchain.prf(69): system(execute) requires one or two arguments.
  Project ERROR: Cannot run compiler 'g++'. Output:
  ===================
  ===================</pre>
  
  <p>Error (when trying to create a new project)</p>
  
  <pre> Maybe you forgot to setup the environment?
  Error while parsing file /workspace/testQt/testQt.pro. Giving up.
  /Qt/5.9.5/gcc_64/mkspecs/features/toolchain.prf(69): system(execute) requires one or two arguments.
  Project ERROR: Cannot run compiler 'g++'. Output:
  ===================
  ===================</pre>
  
  <p>Other details:</p>
  
  <pre>
  Qt version: Qt 5.9.5(gcc_64)
  Compilier: GCC 7.3.0
  OS: Ubuntu 16.04.4 LTS
  </pre>
  
  <p>PS: I had this same error two days back. Reinstalling Qt fixed it but not anymore. </p>
  
  <p>There is no problem with g++. I complied a code with the same complier (used here) through terminal and it works perfectly. </p>
  
  <p>Thank you.</p>