To appease gcc-14's -Wcalloc-transposed-args check.

Follow-up for 2a9ab09.

This gets enabled by default in gcc-14 and complains everywhere where we
use assert() on an expression that is always true (i.e. using
`int x[static 2]` in function declaration, etc.):

[153/2414] Compiling C object src/basic/libbasic.a.p/fs-util.c.o
In file included from ../src/basic/macro.h:13,
                 from ../src/basic/alloc-util.h:10,
                 from ../src/basic/fs-util.c:11:
../src/basic/fd-util.h: In function ‘format_proc_fd_path’:
../src/fundamental/macro-fundamental.h:74:41: warning: ‘nonnull’ argument ‘buf’ compared to NULL [-Wnonnull-compare]
   74 | #define _unlikely_(x) (__builtin_expect(!!(x), 0))
      |                                         ^~~~~
../src/basic/macro.h:150:21: note: in expansion of macro ‘_unlikely_’
  150 |                 if (_unlikely_(!(expr)))                                \
      |                     ^~~~~~~~~~
../src/basic/macro.h:167:22: note: in expansion of macro ‘assert_message_se’
  167 | #define assert(expr) assert_message_se(expr, #expr)
      |                      ^~~~~~~~~~~~~~~~~
../src/basic/fd-util.h:129:9: note: in expansion of macro ‘assert’
  129 |         assert(buf);
      |         ^~~~~~

Disabling this selectively only for asserts is a bit painful, since the
option is not available in all compilers, and it'd need to be handled in
the EFI stuff as well.

So gcc-14 doesn't complain we're out of bounds on the last iteration:

[2092/2414] Compiling C object test-macro.p/src_test_test-macro.c.o
In file included from ../src/basic/list.h:209,
                 from ../src/basic/log.h:10,
                 from ../src/test/test-macro.c:5:
../src/test/test-macro.c: In function ‘test_FOREACH_VA_ARGS’:
../src/basic/macro.h:395:90: warning: array subscript 1 is outside array bounds of ‘uint8_t[1]’ {aka ‘unsigned char[1]’} [-Warray-bounds=]
  395 |              ((long)(_current_ - _entries_) < (long)ELEMENTSOF(_entries_)) && ({ entry = *_current_; true; }); \
../src/basic/macro.h:392:9: note: in expansion of macro ‘_VA_ARGS_FOREACH’
  392 |         _VA_ARGS_FOREACH(entry, UNIQ_T(_entries_, UNIQ), UNIQ_T(_current_, UNIQ), ##__VA_ARGS__)
      |         ^~~~~~~~~~~~~~~~
../src/test/test-macro.c:322:9: note: in expansion of macro ‘VA_ARGS_FOREACH’
  322 |         VA_ARGS_FOREACH(u8, 0) {
      |         ^~~~~~~~~~~~~~~
../src/fundamental/macro-fundamental.h:163:37: note: at offset 1 into object ‘__unique_prefix__entries_181’ of size 1
  163 | #define UNIQ_T(x, uniq) CONCATENATE(__unique_prefix_, CONCATENATE(x, uniq))
      |                                     ^~~~~~~~~~~~~~~~
../src/basic/macro.h:394:28: note: in definition of macro ‘_VA_ARGS_FOREACH’
  394 |         for (typeof(entry) _entries_[] = { __VA_ARGS__ }, *_current_ = _entries_; \
      |                            ^~~~~~~~~
../src/fundamental/macro-fundamental.h:109:27: note: in expansion of macro ‘XCONCATENATE’
  109 | #define CONCATENATE(x, y) XCONCATENATE(x, y)
      |                           ^~~~~~~~~~~~
../src/fundamental/macro-fundamental.h:163:25: note: in expansion of macro ‘CONCATENATE’
  163 | #define UNIQ_T(x, uniq) CONCATENATE(__unique_prefix_, CONCATENATE(x, uniq))
      |                         ^~~~~~~~~~~
../src/basic/macro.h:392:33: note: in expansion of macro ‘UNIQ_T’
  392 |         _VA_ARGS_FOREACH(entry, UNIQ_T(_entries_, UNIQ), UNIQ_T(_current_, UNIQ), ##__VA_ARGS__)
      |                                 ^~~~~~
../src/test/test-macro.c:322:9: note: in expansion of macro ‘VA_ARGS_FOREACH’
  322 |         VA_ARGS_FOREACH(u8, 0) {
      |         ^~~~~~~~~~~~~~~