Hide all malloc functions from compiler [BZ #32366]

Since -1 isn't a power of two, compiler may reject it, hide memalign from
Clang 19 which issues an error:

tst-memalign.c:86:31: error: requested alignment is not a power of 2 [-Werror,-Wnon-power-of-two-alignment]
   86 |   p = memalign (-1, pagesize);
      |                 ^~
tst-memalign.c:86:31: error: requested alignment must be 4294967296 bytes or smaller; maximum alignment assumed [-Werror,-Wbuiltin-assume-aligned-alignment]
   86 |   p = memalign (-1, pagesize);
      |                 ^~

Update tst-malloc-aux.h to hide all malloc functions and include it in
all malloc tests to prevent compiler from optimizing out any malloc
functions.

Tested with Clang 19.1.5 and GCC 15 20241206 for BZ #32366.

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

malloc/tst-valloc.c

@@ -23,6 +23,8 @@
 #include <unistd.h>
 #include <libc-diag.h>
 
+#include "tst-malloc-aux.h"
+
 static int errors = 0;
 
 static void