Use __NR_rt_sigaction instead of __NR_sigaction

__NR_sigaction is not defined on arm64/x64/etc (or rather, it's defined
in unistd-32.h instead of unistd.h).

Patch by Chris Hopman <cjhopman@chromium.org>
Review URL: https://breakpad.appspot.com/10724002/


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1443 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/linux/handler/exception_handler.cc

@@ -200,7 +200,7 @@ void InstallDefaultHandler(int sig) {
   sigemptyset(&sa.sa_mask);
   sa.sa_handler = SIG_DFL;
   sa.sa_flags = SA_RESTART;
-  syscall(__NR_sigaction, sig, &sa, NULL);
+  syscall(__NR_rt_sigaction, sig, &sa, NULL);
 #else
   signal(sig, SIG_DFL);
 #endif