signal: Add __libc_sigaction

The generic implementation basically handle the system agnostic logic
(filtering out the invalid signals) while the __libc_sigaction is
the function with implements the system and architecture bits.

Checked on x86_64-linux-gnu and i686-linux-gnu.

sysdeps/unix/sysv/linux/sparc/sparc32/libc_sigaction.c

@@ -0,0 +1,37 @@
+/* POSIX.1 sigaction call for Linux/SPARC.
+   Copyright (C) 1997-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Miguel de Icaza <miguel@nuclecu.unam.mx>, 1997.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <syscall.h>
+#include <sys/signal.h>
+#include <errno.h>
+#include <kernel_sigaction.h>
+#include <sysdep.h>
+
+void __rt_sigreturn_stub (void);
+void __sigreturn_stub (void);
+
+#define STUB(act, sigsetsize) \
+  (act) ? ((unsigned long)((act->sa_flags & SA_SIGINFO)	\
+			    ? &__rt_sigreturn_stub	\
+			    : &__sigreturn_stub) - 8)	\
+	: 0,						\
+  (sigsetsize)
+
+#include <sysdeps/unix/sysv/linux/libc_sigaction.c>