pasta: Check for zero d_reclen returned by getdents64() syscall

Seen on PPC with some older kernel versions: we seemingly have bytes
left to read from the returned array of dirent structs, but d_reclen
is zero: this, and all the subsequent entries, are not valid.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

pasta.c

@@ -63,7 +63,7 @@ loop:
 		struct dirent *dp = (struct dirent *)buf;
 		int pos = 0;
 
-		while (pos < n) {
+		while (dp->d_reclen && pos < n) {
 			pid_t pid;
 
 			errno = 0;