Fix building of glow on GCC 8.2

class-memaccess generates an error by default on newer versions of GCC and glm uses this a lot.

CMakeLists.txt

@@ -82,6 +82,7 @@ if(NOT MSVC)
         )
     if(GCC)
         target_compile_options(glow PRIVATE -Wdouble-promotion)
+        target_compile_options(glow PUBLIC -Wno-error=class-memaccess)
     else()
         # clang supports this only at newer version
     endif()