Build with clang, and the core and store on macOS, again

Apple clang 21 (an M3) and clang 19 refused what gcc let pass (research
029):
- PURE_FIELD_REST was an enum of UINT32_MAX, past an int (C17): a macro.
- a store's publish copied an entry rebuild left unset when the record
  was not found (the copy was never used): copied when it was made.
- the log's image writer kept a count only Linux's sync_file_range uses.
- ",{" + (row == from) read as adding an int to a string: said plainly.
- the tests: mkdtemp, hidden by _POSIX_C_SOURCE on macOS, needs
  _DARWIN_C_SOURCE; a string split so that \x80 and a stay apart is
  bracketed; a count left over and a malloc measure only glibc has.
The core's and the store's tests pass on the Mac.

1 files changed, 3 insertions, 0 deletions

diff --git a/store/test-tree-store.c b/store/test-tree-store.c
index 2ef9d22..2ffbc39 100644
--- a/store/test-tree-store.c
+++ b/store/test-tree-store.c
@@ -1,4 +1,7 @@
 #define _POSIX_C_SOURCE 200809L
+#ifdef __APPLE__
+#define _DARWIN_C_SOURCE /* mkdtemp, which _POSIX_C_SOURCE hides there */
+#endif
 #include "store.h"
 #include "state.h"
 #include <assert.h>