tst-atomic.c: Mark as UNSUPPORTED when compiled with Clang

tst-atomic.c: Mark as UNSUPPORTED when compiled with Clang

Since Clang can't remove the dead statement and issues an error:

tst-atomic.c:463:7: error: unsupported inline asm: input with type 'int64_t' (aka 'long') matching output with type 'typeof (*&mem)' (aka 'int')
  463 |   if (catomic_exchange_and_add (&mem, 11) != 2
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:213:3: note: expanded from macro 'catomic_exchange_and_add'
  213 |   __arch_exchange_and_add_body (__arch_exchange_and_add_cprefix, __arch_c,    \
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  214 |                                 mem, value)
      |                                 ~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:199:12: note: expanded from macro '__arch_exchange_and_add_body'
  198 |                          : "=r" (__result), "=m" (*mem)                       \
      |                                  ~~~~~~~~
  199 |                          : "0" ((int64_t) cast_to_integer (__addval)),     \
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tst-atomic.c:487:7: error: unsupported inline asm: input with type 'int64_t' (aka 'long') matching output with type 'typeof (*(&mem))' (aka 'int')
  487 |   if (catomic_increment_val (&mem) != 3)
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/atomic.h:313:38: note: expanded from macro 'catomic_increment_val'
  313 | # define catomic_increment_val(mem) (catomic_exchange_and_add ((mem), 1) + 1)
      |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:213:3: note: expanded from macro 'catomic_exchange_and_add'
  213 |   __arch_exchange_and_add_body (__arch_exchange_and_add_cprefix, __arch_c,    \
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  214 |                                 mem, value)
      |                                 ~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:199:12: note: expanded from macro '__arch_exchange_and_add_body'
  198 |                          : "=r" (__result), "=m" (*mem)                       \
      |                                  ~~~~~~~~
  199 |                          : "0" ((int64_t) cast_to_integer (__addval)),     \
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tst-atomic.c:501:7: error: unsupported inline asm: input with type 'int64_t' (aka 'long') matching output with type 'typeof (*(&mem))' (aka 'int')
  501 |   if (catomic_decrement_val (&mem) != 15)
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/atomic.h:340:38: note: expanded from macro 'catomic_decrement_val'
  340 | # define catomic_decrement_val(mem) (catomic_exchange_and_add ((mem), -1) - 1)
      |                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:213:3: note: expanded from macro 'catomic_exchange_and_add'
  213 |   __arch_exchange_and_add_body (__arch_exchange_and_add_cprefix, __arch_c,    \
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  214 |                                 mem, value)
      |                                 ~~~~~~~~~~~
../sysdeps/x86/atomic-machine.h:199:12: note: expanded from macro '__arch_exchange_and_add_body'
  198 |                          : "=r" (__result), "=m" (*mem)                       \
      |                                  ~~~~~~~~
  199 |                          : "0" ((int64_t) cast_to_integer (__addval)),     \
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mark tst-atomic.c as UNSUPPORTED when compiled with Clang.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>