VECGEOM-35 Proper use of ATOMIC_FLAG_INIT
ATOMIC_FLAG_INIT is to be used for initialization via assignement.
See http://en.cppreference.com/w/cpp/atomic/atomic_flag
Otherwise you get warnings like:
TLS.h:135:31 warning: braces around scalar initializer [-Wbraced-scalar-init] static std::atomic_flag gLock(ATOMIC_FLAG_INIT); ^~~~~~~~~~~~~~~~ ...../include/c++/v1/atomic:1779:26: note: expanded from macro 'ATOMIC_FLAG_INIT' #define ATOMIC_FLAG_INIT {false} ^~~~~~~
on some platforms.