remove empty qlock.c

src/libthread/mkfile

diff --git a/src/libthread/mkfile b/src/libthread/mkfile
index 9809378..0be8aec 100644
--- a/src/libthread/mkfile
+++ b/src/libthread/mkfile
@@ -7,7 +7,6 @@
 	ioproc.$O\
 	iorw.$O\
 	pthread.$O\
-	qlock.$O\
 	ref.$O\
 	thread.$O\
 

src/libthread/qlock.c

diff --git a/src/libthread/qlock.c b/src/libthread/qlock.c
deleted file mode 100644
index 30a0c9e..0000000
--- a/src/libthread/qlock.c
+++ /dev/null
@@ -1,3 +0,0 @@
-#include "u.h"
-#include "libc.h"
-