flex: fix build with gcc-15 on host

* fixes:
  http://errors.yoctoproject.org/Errors/Details/853017/

../../flex-2.6.4/src/../lib/malloc.c:6:12: warning: conflicting types for built-in function ‘malloc’; expected ‘void *(long unsigned int)’ [-Wbuiltin-declaration-mismatch]
    6 |      void *malloc ();
      |            ^~~~~~
../../flex-2.6.4/src/../lib/malloc.c:5:1: note: ‘malloc’ is declared in header ‘<stdlib.h>’
    4 |      #include <sys/types.h>
  +++ |+#include <stdlib.h>
    5 |
../../flex-2.6.4/src/../lib/malloc.c: In function ‘rpl_malloc’:
../../flex-2.6.4/src/../lib/malloc.c:16:15: error: too many arguments to function ‘malloc’; expected 0, have 1
   16 |        return malloc (n);
      |               ^~~~~~  ~
../../flex-2.6.4/src/../lib/malloc.c:6:12: note: declared here
    6 |      void *malloc ();
      |            ^~~~~~
make[2]: *** [Makefile:1431: ../lib/stage1flex-malloc.o] Error 1

(From OE-Core rev: e1832f02d70bd4082bc82ae2983546c880818491)

Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/flex/flex/0001-Match-malloc-signature-to-its-use.patch

@@ -0,0 +1,25 @@
+From cec508013706ef06dbac036905a90cbe075fa03d Mon Sep 17 00:00:00 2001
+From: Richard Barnes <rbarnes@umn.edu>
+Date: Wed, 2 Oct 2024 10:35:09 -0700
+Subject: [PATCH] Match `malloc` signature to its use
+
+Upstream-Status: Submitted [https://github.com/westes/flex/pull/674]
+
+Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
+---
+ lib/malloc.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/lib/malloc.c b/lib/malloc.c
+index 75e8ef9..701b9b3 100755
+--- a/lib/malloc.c
++++ b/lib/malloc.c
+@@ -3,7 +3,7 @@
+      
+      #include <sys/types.h>
+      
+-     void *malloc ();
++     void *malloc (size_t n);
+      
+      /* Allocate an N-byte block of memory from the heap.
+         If N is zero, allocate a 1-byte block.  */

meta/recipes-devtools/flex/flex_2.6.4.bb

@@ -19,6 +19,7 @@ SRC_URI = "${GITHUB_BASE_URI}/download/v${PV}/flex-${PV}.tar.gz \
            file://check-funcs.patch \
            file://0001-Emit-no-line-directives-if-gen_line_dirs-is-false.patch \
            file://0001-build-tests-add-missing-parser-scanner-dependencies.patch \
+           file://0001-Match-malloc-signature-to-its-use.patch \
            "
 
 SRC_URI[md5sum] = "2882e3179748cc9f9c23ec593d6adc8d"