re PR go/81324 (libgo does not build with glibc 2.18)

	PR go/81324
    sysinfo.c: ignore ptrace_peeksiginfo_args from <linux/ptrace.h>
    
    With some versions of glibc and GNU/Linux ptrace_pseeksiginfo_args is
    defined in both <sys/ptrace.h> and <linux/ptrace.h>. We don't actually
    care about the struct, so use a #define to avoid a redefinition error.
    
    This fixes https://gcc.gnu.org/PR81324.
    
    Reviewed-on: https://go-review.googlesource.com/49290

From-SVN: r250324

gcc/go/gofrontend/MERGE

-2ae6bf76f97f7d4c63a1f0ad0683b9ba62baaf06
+21775ae119830810d9e415a02e85349f4190c68c
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/sysinfo.c

@@ -106,9 +106,13 @@
 /* Avoid https://sourceware.org/bugzilla/show_bug.cgi?id=762 .  */
 #define ia64_fpreg pt_ia64_fpreg
 #define pt_all_user_regs pt_ia64_all_user_regs
+/* Avoid redefinition of ptrace_peeksiginfo from <sys/ptrace.h>.
+   https://gcc.gnu.org/PR81324 .  */
+#define ptrace_peeksiginfo_args ignore_ptrace_peeksiginfo_args
 #include <linux/ptrace.h>
 #undef ia64_fpreg
 #undef pt_all_user_regs
+#undef ptrace_peeksiginfo_args
 #endif
 #if defined(HAVE_LINUX_RTNETLINK_H)
 #include <linux/rtnetlink.h>