Download the Windows compiler

We use this for building code to run on the driver's station.

Change-Id: I03cb907f67419e45a3a7204fa61ba2dd73b6687c
diff --git a/motors/pistol_grip/BUILD b/motors/pistol_grip/BUILD
index 0a24ba8..75cab98 100644
--- a/motors/pistol_grip/BUILD
+++ b/motors/pistol_grip/BUILD
@@ -80,6 +80,7 @@
     output_to_bindir = True,
     tools = [
         "usb_forward_windows_build.sh",
+        "@mingw_compiler//:all_files",
     ],
 )