package/libcap: backport upstream patch to fix build on Xtensa

Following the bump of libcap to version 2.76 in commit
e2eb2ee58b9f70ebb83231537cca19bd28fa48de, the build started failing on
Xtensa. The bug was reported upstream at
https://bugzilla.kernel.org/show_bug.cgi?id=219915 and was
subsequently fixed by upstream commit:

  https://git.kernel.org/pub/scm/libs/libcap/libcap.git/commit/?id=6cdd8cd72ebcedd6b1b6c989a7e5722d5d87f35c

Which we backport in this commit.

Fixes:

  https://autobuild.buildroot.org/results/b9ff9258f407898eeee80dd8cc4dd1d777f44c06

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/libcap/0002-Support-for-__xtensa__-architecture.patch

@@ -0,0 +1,65 @@
+From 9421f4ff93c341482d3aa4a0cd57aba1978bdd62 Mon Sep 17 00:00:00 2001
+From: "Andrew G. Morgan" <morgan@kernel.org>
+Date: Sat, 19 Apr 2025 08:00:23 -0700
+Subject: [PATCH] Support for __xtensa__ architecture.
+
+It looks like __xtensa__ defines SA_RESTORER, but my read of the
+kernel code suggests that signal handling does not require it be
+set. Specifically, if the SA_RESTORER flag is not set, the kernel
+inserts a sys_rt_sigreturn call into the stack frame.
+
+Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
+Upstream: 6cdd8cd72ebcedd6b1b6c989a7e5722d5d87f35c
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+---
+ psx/psx_calls.c | 13 +++++++------
+ 1 file changed, 7 insertions(+), 6 deletions(-)
+
+diff --git a/psx/psx_calls.c b/psx/psx_calls.c
+index 8195964..aff105f 100644
+--- a/psx/psx_calls.c
++++ b/psx/psx_calls.c
+@@ -49,7 +49,8 @@
+     || defined(__powerpc__) || defined(__s390__) || defined(__riscv) \
+     || defined(__alpha__) || defined(__hppa__) || defined(__sh__) \
+     || defined(__m68k__) || defined(__sparc__) || defined(__arc__) \
+-    || defined(__microblaze__) || defined(__or1k__)
++    || defined(__microblaze__) || defined(__or1k__) \
++    || defined(__xtensa__)
+ 
+ #undef _NSIG
+ #undef _NSIG_BPW
+@@ -69,8 +70,7 @@
+ #define _NSIG_WORDS  (_NSIG / _NSIG_BPW)
+ 
+ #if defined(__x86_64__) || defined(__i386__) \
+-    || defined(__arm__) \
+-    || defined(__powerpc__) \
++    || defined(__arm__) || defined(__powerpc__) \
+     || defined(__arc__)
+ /* field used */
+ #define SA_RESTORER  0x04000000
+@@ -78,8 +78,9 @@
+ 
+ #if defined(SA_RESTORER) \
+     || defined(__aarch64__) \
+-    || defined(__m68k__) || defined(__sh__) || defined(__sparc__) \
+-    || defined(__s390__) || defined(__sparc__)
++    || defined(__m68k__) || defined(__sh__) \
++    || defined(__s390__) || defined(__sparc__) \
++    || defined(__xtensa__)
+ /* field defined */
+ #define _HAS_SA_RESTORER   void *sa_restorer;
+ #else
+@@ -93,7 +94,7 @@ typedef struct {
+ #define sigset_t psx_sigset_t
+ 
+ struct psx_sigaction {
+-#if defined(__m68k__) || defined(__alpha__)
++#if defined(__m68k__) || defined(__alpha__) || defined(__xtensa__)
+     void *sa_handler;
+     sigset_t sa_mask;
+     unsigned long sa_flags;
+-- 
+2.49.0
+