build: add all-qemu.bash, handful of arm fixes

R=r
CC=golang-dev
https://golang.org/cl/4313051
diff --git a/src/pkg/runtime/linux/arm/signal.c b/src/pkg/runtime/linux/arm/signal.c
index bf4cb48..05c6b02 100644
--- a/src/pkg/runtime/linux/arm/signal.c
+++ b/src/pkg/runtime/linux/arm/signal.c
@@ -135,6 +135,8 @@
 		sa.sa_flags |= SA_RESTART;
 	sa.sa_mask = ~0ULL;
 	sa.sa_restorer = (void*)runtime·sigreturn;
+	if(fn == runtime·sighandler)
+		fn = (void*)runtime·sigtramp;
 	sa.sa_handler = fn;
 	runtime·rt_sigaction(i, &sa, nil, 8);
 }