update_engine: Update for new location for brillo processes

These files have moved into a subdirectory. Update the code so they can
still be found.

BUG=chromium:1085464
TEST=emerge-nami update_engine
Will also use pre-CQ

Change-Id: I85d89b6efa960e77bb56f67ab432c734e8fea8ea
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2212760
Tested-by: Simon Glass <sjg@chromium.org>
Commit-Queue: Simon Glass <sjg@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/common/subprocess.cc b/common/subprocess.cc
index 45dff92..ff37472 100644
--- a/common/subprocess.cc
+++ b/common/subprocess.cc
@@ -32,7 +32,7 @@
 #include <base/stl_util.h>
 #include <base/strings/string_util.h>
 #include <base/strings/stringprintf.h>
-#include <brillo/process.h>
+#include <brillo/process/process.h>
 #include <brillo/secure_blob.h>
 
 #include "update_engine/common/utils.h"