linux-user: remove signal handler before calling abort()

Qemu may hang in host_signal_handler after qemu has done a
seppuku with cpu_abort(). But at this stage we are not really
interested in target process coredump anymore, so unregister
host_signal_handler to die grafefully.
Signed-off-by: NRiku Voipio <riku.voipio@nokia.com>

exec.c

@@ -40,6 +40,7 @@
 #include "kvm.h"
 #if defined(CONFIG_USER_ONLY)
 #include <qemu.h>
+#include <signal.h>
 #endif
 
 //#define DEBUG_TB_INVALIDATE
@@ -1692,6 +1693,14 @@ void cpu_abort(CPUState *env, const char *fmt, ...)
     }
     va_end(ap2);
     va_end(ap);
+#if defined(CONFIG_USER_ONLY)
+    {
+        struct sigaction act;
+        sigfillset(&act.sa_mask);
+        act.sa_handler = SIG_DFL;
+        sigaction(SIGABRT, &act, NULL);
+    }
+#endif
     abort();
 }