Java: add flag_use_atomic_builtins

[Joseph S. Myers]

On Wed, 12 Aug 2009, Andrew Haley wrote:

> Some targets, particularly ARM, don't have instructions for things
> such as sync_compare_and_swap.  Instead, a routine in libgcc is
> used.  This patch adds a new gcj option, -fuse-atomic-builtins,
> which causes gcj to use the routines in libgcc whenever atomic
> operations are needed.

Wouldn't a target hook to allow a target to declare which operations it 
provides in libgcc be better than a command-line option?

-- 
Joseph S. Myers
joseph@codesourcery.com