Fix incorrect relocations for x86.

These calls were not going through the PLT like they should have been.

Bug: 16853291
Change-Id: Id70488b077256a70137c4417f21be2c2d1d4341c
diff --git a/libc/arch-x86_64/syscalls/__ptrace.S b/libc/arch-x86_64/syscalls/__ptrace.S
index 0a64fee..ea88847 100644
--- a/libc/arch-x86_64/syscalls/__ptrace.S
+++ b/libc/arch-x86_64/syscalls/__ptrace.S
@@ -10,7 +10,7 @@
     jb      1f
     negl    %eax
     movl    %eax, %edi
-    call    __set_errno
+    call    PIC_PLT(__set_errno)
 1:
     ret
 END(__ptrace)