CMakeLists.txt: turning off -W-ignored-attributes, there are loads of those with newer GCC, originating from Eigen (https://eigen.tuxfamily.org/bz/show_bug.cgi?id=1221)

CMakeLists.txt

@@ -173,10 +173,11 @@ if (NOT MSVC AND ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_CXX_COMP
     # On GCC and Clang, no return from a non-void function is a warning only. Here, we make it an error.
     add_compile_options(-Werror=return-type)
 
-    #removes LOTS of extraneous Eigen warnings (GCC only supports it since 6.1)
-    #if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 6.1)
-        # add_compile_options(-Wno-ignored-attributes) # Tamas: Eigen include dirs are marked as SYSTEM
-    #endif()
+    # removes LOTS of extraneous Eigen warnings (GCC only supports it since 6.1)
+    # https://eigen.tuxfamily.org/bz/show_bug.cgi?id=1221
+    if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" OR CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 6.0)
+        add_compile_options(-Wno-ignored-attributes) # Tamas: Eigen include dirs are marked as SYSTEM
+    endif()
 
     #GCC generates loads of -Wunknown-pragmas when compiling igl. The fix is not easy due to a bug in gcc, see
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66943 or