conform: XFAIL siginfo_t si_band test on sparc64

We can use long int on sparcv9, but on sparc64, we must match the int
type used by the kernel (and not long int, as in POSIX).

sysdeps/unix/sysv/linux/sparc/bits/siginfo-arch.h

@@ -2,7 +2,12 @@
 #ifndef _BITS_SIGINFO_ARCH_H
 #define _BITS_SIGINFO_ARCH_H 1
 
-#define __SI_BAND_TYPE int
+/* The kernel uses int instead of long int (as in POSIX).  In 32-bit
+   mode, we can still use long int, but in 64-bit mode, we need to
+   deviate from POSIX.  */
+#if __WORDSIZE == 64
+# define __SI_BAND_TYPE int
+#endif
 
 #define __SI_SIGFAULT_ADDL \
   int _si_trapno;

sysdeps/unix/sysv/linux/sparc/sparc64/Makefile

@@ -7,3 +7,8 @@ LD += -melf64_sparc
 ifeq ($(subdir),stdlib)
 sysdep_routines += __start_context
 endif
+
+ifeq ($(subdir),conform)
+# For bug 23821 (incorrect type of si_band).
+conformtest-xfail-conds += sparc64-linux
+endif