use syscall in forkt

a6061522 · Nickolai Zeldovich · beed8e04 · a6061522
--- a/lib/uthread.S
+++ b/lib/uthread.S
@@ -13,7 +13,7 @@ forkt:

        movq $1, %rdi           # flag for sys_fork
        movq $SYS_fork, %rax
-        int $T_SYSCALL
+        syscall

        cmpq $0, %rax           # pid/tid
        jne 1f