Make vulkan build with the VNDK.

When the vndk is enabled (BOARD_VNDK_VERSION=current),
vendor libraries must only link against vendor variants
in the build system. This also means that they receive
restricted sets of headers and that automatic global
headers are restricted.

Test: build vulkan with BOARD_VNDK_VERSION=current
Bug: 37342627
Change-Id: I9690635e4654e053cf35a3941aff14f4f7b46491
diff --git a/vulkan/nulldrv/null_driver.cpp b/vulkan/nulldrv/null_driver.cpp
index 6714779..a3da651 100644
--- a/vulkan/nulldrv/null_driver.cpp
+++ b/vulkan/nulldrv/null_driver.cpp
@@ -19,12 +19,12 @@
 #include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <algorithm>
 #include <array>
 
 #include <log/log.h>
-#include <utils/Errors.h>
 
 #include "null_driver_gen.h"