Redundant C++ standard check

[AntoinePrv]

This check:

xeus-cookiecutter/{{cookiecutter.github_project_name}}/CMakeLists.txt

Line 115 in 0086213

CHECK_CXX_COMPILER_FLAG("-std=c++{{cookiecutter.cpp_standard}}" HAS_CPP_{{cookiecutter.cpp_standard}}_FLAG)

Seems to be redundant with this one:

xeus-cookiecutter/{{cookiecutter.github_project_name}}/CMakeLists.txt

Line 177 in 0086213

CHECK_CXX_COMPILER_FLAG("-std=c++{{cookiecutter.cpp_standard}}" HAS_CPP_{{cookiecutter.cpp_standard}}_FLAG)

Which is itself redundant with target_compile_features, as this function already check if the feature is supported by the compiler, as show in this example:

 CMake Error at CMakeLists.txt:154 (target_compile_features):
  target_compile_features The compiler feature "cxx_std_23" is not known to
  CXX compiler

  "GNU"

  version 10.4.0.

[DerThorsten]

Thanks for reporting this, feel free to send a PR