Fix missing variable

It seems like no one has tried to compile on a platform without
`setsid` for almost a quarter of a century.

1 files changed, 1 insertions, 1 deletions

diff --git a/process.c b/process.c
index 11d5fc999c..b1f9931f06 100644
--- a/process.c
+++ b/process.c
@@ -5258,7 +5258,7 @@ static rb_pid_t
 ruby_setsid(void)
 {
     rb_pid_t pid;
-    int ret;
+    int ret, fd;
 
     pid = getpid();
 #if defined(SETPGRP_VOID)