[newlib-cygwin] Phoenix-RTOS: Fix warning with pointer treated as integer.

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e5e0bd38d2c62cdb06d143c547a6d80f5ac6a941

commit e5e0bd38d2c62cdb06d143c547a6d80f5ac6a941
Author: Kuba Sejdak <jakub.sejdak@phoesys.com>
Date:   Fri Jun 24 14:14:49 2016 +0200

    Phoenix-RTOS: Fix warning with pointer treated as integer.

Diff:
---
 newlib/libc/sys/phoenix/groups.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/newlib/libc/sys/phoenix/groups.c b/newlib/libc/sys/phoenix/groups.c
index 11cc079..b231475 100644
--- a/newlib/libc/sys/phoenix/groups.c
+++ b/newlib/libc/sys/phoenix/groups.c
@@ -96,5 +96,5 @@ int setpgrp(pid_t pid, pid_t pgid)
 {
 	/* TODO: implement. */
 	errno = ENOSYS;
-	return NULL;
+	return -1;
 }