Increase minimum required CMake version to 3.8
Value 17
for CXX_STANDARD
was added in CMAke .8 and is not supported in 3.7.
See https://cmake.org/cmake/help/latest/prop_tgt/CXX_STANDARD.html
Value 17
for CXX_STANDARD
was added in CMAke .8 and is not supported in 3.7.
See https://cmake.org/cmake/help/latest/prop_tgt/CXX_STANDARD.html