Drive code works on Tantrum.

Need to write the spring code.  Drive now supports doubles...  What a
pain.

Change-Id: Id589acdc443dcd81242a21e3b0c26f81d6974dc8
diff --git a/frc971/BUILD b/frc971/BUILD
index 4729bf6..46317d3 100644
--- a/frc971/BUILD
+++ b/frc971/BUILD
@@ -1,15 +1,18 @@
-package(default_visibility = ['//visibility:public'])
+package(default_visibility = ["//visibility:public"])
+
+load("//tools:environments.bzl", "mcu_cpus")
 
 cc_library(
-  name = 'shifter_hall_effect',
-  hdrs = [
-    'shifter_hall_effect.h',
-  ],
+    name = "shifter_hall_effect",
+    hdrs = [
+        "shifter_hall_effect.h",
+    ],
+    compatible_with = mcu_cpus,
 )
 
 cc_library(
-  name = 'constants',
-  hdrs = [
-    'constants.h',
-  ],
+    name = "constants",
+    hdrs = [
+        "constants.h",
+    ],
 )