Explicitly build 'define_catch_main.cpp' with c++17.

Author: helmesjo

CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.8)
 
 option(PIPEABLE_BUILD_TESTS "Build tests" OFF)
 
-project(pipeable)
+project(pipeable CXX)
 
 add_library( ${PROJECT_NAME} INTERFACE)
 add_library(fho::${PROJECT_NAME} ALIAS ${PROJECT_NAME})

catch2/CMakeLists.txt

@@ -4,4 +4,5 @@ add_library(catch2 define_main.cpp)
 target_include_directories( catch2 
     PRIVATE ./catch2
     INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
-)
+)
+target_compile_features(catch2 PUBLIC cxx_std_17)