package/libffi: fix host build failure

Host build fails on updated Arch Linux desktop.

My current /usr/bin/gcc version is 14.1.1 20240522, where
implicit-function-declaration cause build to fail:

2024-06-05T07:03:20 libtool: compile:  /home/roy/hymatek/connexi-touchpanel-firmware/mxxf1/output/host/bin/ccache /usr/bin/gcc -DHAVE_CONFIG_H -I. -I.. -I. -I../include -Iinclude -I../src -I/home/roy/hymatek/connexi-touchpanel-firmware/mxxf1/output/host/include -Wall -O2 -I/home/roy/hymatek/connexi-touchpanel-firmware/mxxf1/output/host/include -fexceptions -c ../src/tramp.c  -fPIC -DPIC -o src/.libs/tramp.o
2024-06-05T07:03:20 ../src/tramp.c: In function ‘ffi_tramp_get_temp_file’:
2024-06-05T07:03:20 ../src/tramp.c:262:22: error: implicit declaration of function ‘open_temp_exec_file’ [-Wimplicit-function-declaration]
2024-06-05T07:03:20 262 |   tramp_globals.fd = open_temp_exec_file ();
2024-06-05T07:03:20 |                      ^~~~~~~~~~~~~~~~~~~

Patch from master was added to fix build.

Signed-off-by: Roy Kollen Svendsen <roy.kollen.svendsen@akersolutions.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libffi/0004-Forward-declare-open_temp_exec_file-764.patch

@@ -0,0 +1,49 @@
+From ce077e5565366171aa1b4438749b0922fce887a4 Mon Sep 17 00:00:00 2001
+From: serge-sans-paille <serge.guelton@telecom-bretagne.eu>
+Date: Thu, 2 Feb 2023 14:46:29 +0000
+Subject: [PATCH] Forward declare open_temp_exec_file (#764)
+
+It's defined in closures.c and used in tramp.c.
+Also declare it as an hidden symbol, as it should be.
+
+Co-authored-by: serge-sans-paille <sguelton@mozilla.com>
+Upstream: https://github.com/libffi/libffi/pull/764
+Signed-off-by: Roy Kollen Svendsen <roy.kollen.svendsen@akersolutions.com>
+---
+ include/ffi_common.h | 4 ++++
+ src/tramp.c          | 4 ++++
+ 2 files changed, 8 insertions(+)
+
+diff --git a/include/ffi_common.h b/include/ffi_common.h
+index 2bd31b0..c53a794 100644
+--- a/include/ffi_common.h
++++ b/include/ffi_common.h
+@@ -128,6 +128,10 @@ void *ffi_data_to_code_pointer (void *data) FFI_HIDDEN;
+    static trampoline. */
+ int ffi_tramp_is_present (void *closure) FFI_HIDDEN;
+ 
++/* Return a file descriptor of a temporary zero-sized file in a
++   writable and executable filesystem. */
++int open_temp_exec_file(void) FFI_HIDDEN;
++
+ /* Extended cif, used in callback from assembly routine */
+ typedef struct
+ {
+diff --git a/src/tramp.c b/src/tramp.c
+index 7e005b0..5f19b55 100644
+--- a/src/tramp.c
++++ b/src/tramp.c
+@@ -39,6 +39,10 @@
+ #ifdef __linux__
+ #define _GNU_SOURCE 1
+ #endif
++
++#include <ffi.h>
++#include <ffi_common.h>
++
+ #include <stdio.h>
+ #include <unistd.h>
+ #include <stdlib.h>
+-- 
+2.45.1
+