Remove now-unused configure checks

Author: morrisonlevi

Zend/Zend.m4

@@ -389,32 +389,3 @@ AC_LINK_IFELSE([AC_LANG_PROGRAM([[
 if test "$ac_cv_cpuid_count_available" = "yes"; then
   AC_DEFINE([HAVE_CPUID_COUNT], 1, [whether __cpuid_count is available])
 fi
-
-dnl Check whether <stdatomic.h> is available.
-AC_CACHE_CHECK(
-  [whether <stdatomic.h> is available],
-  ac_cv_stdatomic_h,
-  [AC_RUN_IFELSE(
-    [AC_LANG_SOURCE(
-      [[
-        #include <stdatomic.h>
-        #include <stdbool.h>
-        int main(void) {
-          atomic_bool val = false;
-          (void)atomic_load(&val);
-          atomic_store(&val, true);
-          (void)atomic_exchange(&val, false);
-
-          if (sizeof(atomic_bool) != sizeof(bool)) return 1;
-          if (_Alignof(atomic_bool) != _Alignof(bool)) return 1;
-          return 0;
-        }
-      ]]
-    )],
-    [ac_cv_stdatomic_h_available=yes],
-    [ac_cv_stdatomic_h_available=no]
-  )]
-)
-if test "$ac_cv_stdatomic_h_available" = "yes"; then
-  AC_DEFINE([HAVE_STDATOMIC_H], 1, [whether <stdatomic.h> is available])
-fi

Zend/zend_atomic.h

@@ -147,6 +147,7 @@ inline ZEND_API void zend_atomic_bool_store(zend_atomic_bool *obj, bool desired)
  * improvement. As more platforms support C11 atomics, or as we add support
  * for more platforms through intrinsics/asm, this should be used less and
  * less until it can be removed.
+ * At the time of this writing, all platforms in CI avoided this fallback.
  */
 
 inline ZEND_API void zend_atomic_bool_store(zend_atomic_bool *obj, bool desired) {
@@ -163,7 +164,6 @@ inline ZEND_API bool zend_atomic_bool_exchange(zend_atomic_bool *obj, bool desir
 	return prev;
 }
 
-#error Just seeing if any platforms in CI are using this fallback.
 #endif
 
 END_EXTERN_C()