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/bionic/vfork.S b/libc/arch-x86/bionic/vfork.S
index ffa6b16..91453f1 100644
--- a/libc/arch-x86/bionic/vfork.S
+++ b/libc/arch-x86/bionic/vfork.S
@@ -38,7 +38,7 @@
   jb      1f
   negl    %eax
   pushl   %eax
-  call    __set_errno
+  call    PIC_PLT(__set_errno)
 1:
   jmp     *%ecx  // Jump to the stored return address.
 END(vfork)