added -Wno-c++17-extensions for cmake (<3.8) support

CMakeLists.txt

@@ -54,6 +54,11 @@ if(${OPENMP_FOUND})
   set(KOKKOS_ENABLE_OPENMP ON CACHE BOOL "")
 endif()
 
+# Kokkso compiler flags
+add_subdirectory(${PASTIS_SOURCE_DIR}/packages/kokkos)
+include_directories(${Kokkos_INCLUDE_DIRS_RET})
+include(GetKokkosCompilerFlags)
+
 # sets Kokkos debug flags when non release build
 if (CMAKE_BUILD_TYPE MATCHES "Release")
   set (KOKKOS_ENABLE_DEBUG OFF)
@@ -65,16 +70,13 @@ endif()
 if(${CMAKE_VERSION} VERSION_LESS "3.8.0")
   message(WARNING "Please consider to switch to CMake >= 3.8")
   set(PASTIS_CXX_FLAGS "${PASTIS_CXX_FLAGS}  -std=gnu++1z")
+  if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    set(PASTIS_CXX_FLAGS "${PASTIS_CXX_FLAGS}  -Wno-c++17-extensions")
+  endif()
 else()
   set(CMAKE_CXX_STANDARD "17")
 endif()
 
-add_subdirectory(${PASTIS_SOURCE_DIR}/packages/kokkos)
-include_directories(${Kokkos_INCLUDE_DIRS_RET})
-
-# Kokkso compiler flags
-include(GetKokkosCompilerFlags)
-
 # Compiler flags
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${PASTIS_CXX_FLAGS}")