title: Qt Creator can't find CMAKE_CXX_COMPILER compiler in linux mint 64 bit
body: <p>I'm trying to use cmake to build a simple hello world c++ application in Qt Creator 4.7.0-beta1 and I get the following error:</p>
  
  <pre><code>Running "/usr/bin/cmake /home/cpnblank/Documents/vulkandev/cmaketest '-GCodeBlocks - Unix Makefiles' -DCMAKE_CXX_COMPILER:STRING= -DCMAKE_C_COMPILER:STRING=/usr/bin/gcc -DCMAKE_PREFIX_PATH:STRING=/home/cpnblank/Qt/5.11.0/gcc_64 -DQT_QMAKE_EXECUTABLE:STRING=/home/cpnblank/Qt/5.11.0/gcc_64/bin/qmake" in /tmp/QtCreator-CRirhE/qtc-cmake-DuSxtHku.
  -- The C compiler identification is GNU 5.4.0
  -- The CXX compiler identification is unknown
  -- Check for working C compiler: /usr/bin/gcc
  -- Check for working C compiler: /usr/bin/gcc -- works
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Detecting C compile features
  -- Detecting C compile features - done
  CMake Error at CMakeLists.txt:3 (project):
    No CMAKE_CXX_COMPILER could be found.
  </code></pre>
  
  <p>Tell CMake where to find the compiler by setting either the environment
    variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
    to the compiler, or to the compiler name if it is in the PATH.</p>
  
  <p>-- Configuring incomplete, errors occurred!
  See also "/tmp/QtCreator-CRirhE/qtc-cmake-DuSxtHku/CMakeFiles/CMakeOutput.log".
  See also "/tmp/QtCreator-CRirhE/qtc-cmake-DuSxtHku/CMakeFiles/CMakeError.log".
  *** cmake process exited with exit code 1.</p>
  
  <p>I have build-essentials installed, and I have also set the cxx path to g++. I have also uninstalled and reinstalled g++ and gcc.</p>
  
  <p>Any ideas?</p>