More explicitly define systemc patch file path.

Makes it easier to import kelvin_hw to other projects.

Change-Id: I387a51f00f53c9b0bdb50297603972ee4f3875d5

rules/deps.bzl

diff --git a/rules/deps.bzl b/rules/deps.bzl
index 9e359b7..8f1645a 100644
--- a/rules/deps.bzl
+++ b/rules/deps.bzl
@@ -15,7 +15,7 @@
 
     http_archive(
         name = "accellera_systemc",
-        build_file = "systemc.BUILD",
+        build_file = "@kelvin_hw//external:systemc.BUILD",
         sha256 = "bfb309485a8ad35a08ee78827d1647a451ec5455767b25136e74522a6f41e0ea",
         strip_prefix = "systemc-2.3.4",
         urls = [