icu: remove BR2_ARCH_HAS_ATOMICS dependency
The BR2_ARCH_HAS_ATOMICS was added because on ARC, atomic instructions
may not be provided by the architecture and therefore the compiler
does not provide the __sync_*() built-ins.
However, since then, icu was changed and is now able to use C++11
atomics, or even no atomic operations at all. In fact, icu will:
* If possible, it will use C++11 atomics, which internally rely on
the __atomic built-ins. These are available since gcc 4.7, and all
architectures provide it. On some architectures, you *must* link
with libatomic, on some other architectures, they are available
built-in, but in all cases, linking against libatomic does not
harm. Thanks to this, even ARC with no atomic support (which was
the original reason for adding the BR2_ARCH_HAS_ATOMICS) dependency
builds fine, provided -latomic is added to LIBS.
* If C++11 atomics are not available, then it falls back to
__sync_*() built-ins, which allows compilers older than 4.7 to be
supported.
* If really no atomic mechanism is available, then it falls back to a
basic implementation based on a mutex.
Conclusion:
- The BR2_ARCH_HAS_ATOMICS dependency is no longer needed.
- We need to link with -latomic when gcc >= 4.7 is used.
Note that reverse dependencies of icu are also changed accordingly.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Thomas Petazzoni