fix return value in pipe polyfill

Change-Id: I1ddce4b05be5275e0171d8eafaf4e39b3197f522
Reviewed-on: https://chromium-review.googlesource.com/849556
Reviewed-by: Mark Seaborn <mseaborn@chromium.org>
diff --git a/linux_syscall_support.h b/linux_syscall_support.h
index 5d9c2e8..605a368 100644
--- a/linux_syscall_support.h
+++ b/linux_syscall_support.h
@@ -4464,7 +4464,7 @@
 #endif
 
 #if !defined(__NR_pipe)
-  LSS_INLINE pid_t LSS_NAME(pipe)(int *pipefd) {
+  LSS_INLINE int LSS_NAME(pipe)(int *pipefd) {
     return LSS_NAME(pipe2)(pipefd, 0);
   }
 #endif