syscall: fix little-endian assumptions

Change-Id: Ia38256998e544d620a342dabedd9289d61fb0551
Reviewed-on: https://go-review.googlesource.com/9672Reviewed-by: Dave Cheney <dave@cheney.net>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/syscall/exec_linux.go

@@ -178,14 +178,14 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
 	}
 
 	if sys.Foreground {
-		pgrp := sys.Pgid
+		pgrp := int32(sys.Pgid)
 		if pgrp == 0 {
 			r1, _, err1 = RawSyscall(SYS_GETPID, 0, 0, 0)
 			if err1 != 0 {
 				goto childerror
 			}
 
-			pgrp = int(r1)
+			pgrp = int32(r1)
 		}
 
 		// Place process group in foreground.