Use downloaded pandoc instead of relying on it to be installed

Change-Id: I6477b14bafd04b4d44257526c99d816e77661bb0
diff --git a/motors/BUILD b/motors/BUILD
index 50a4bce..395765e 100644
--- a/motors/BUILD
+++ b/motors/BUILD
@@ -43,7 +43,7 @@
         "NOTES.html",
     ],
     cmd = " ".join([
-        "pandoc",
+        "$(location @pandoc)",
         "-f",
         "markdown_github-hard_line_breaks",
         "-t",
@@ -52,6 +52,10 @@
         "$@",
         "$<",
     ]),
+    tools = [
+        "@pandoc",
+        "@pandoc//:all_files",
+    ],
 )
 
 cc_library(