Regen.

configure

@@ -15086,13 +15086,60 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 # Atomics
-ac_fn_c_check_header_compile "$LINENO" "stdatomic.h" "ac_cv_header_stdatomic_h" "$ac_includes_default"
+       for ac_header in stdatomic.h
+do :
+  ac_fn_c_check_header_compile "$LINENO" "stdatomic.h" "ac_cv_header_stdatomic_h" "$ac_includes_default"
 if test "x$ac_cv_header_stdatomic_h" = xyes
 then :
   printf "%s\n" "#define HAVE_STDATOMIC_H 1" >>confdefs.h
+ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether libatomic is required" >&5
+printf %s "checking whether libatomic is required... " >&6; }
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdatomic.h>
+int
+main (void)
+{
+atomic_uint_fast64_t i; i++;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+else $as_nop
+  save_LIBS="$LIBS"
+        LIBS="$LIBS -latomic"
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdatomic.h>
+int
+main (void)
+{
+atomic_uint_fast64_t i; i++;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"
+then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
+else $as_nop
+  as_fn_error $? "failed to find working configuration with atomics" "$LINENO" 5
 
 fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
+    conftest$ac_exeext conftest.$ac_ext
 
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+
+done
 
 # Check for poll.h (it's in POSIX so everyone should have it?)
 ac_fn_c_check_header_compile "$LINENO" "poll.h" "ac_cv_header_poll_h" "$ac_includes_default"