Add BUILD files for IMU board

Change-Id: I5437972c594ecd3ebeb24d9b9b96f2801b405021
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/tools/platforms/hardware/BUILD b/tools/platforms/hardware/BUILD
index b33606a..93c3e27 100644
--- a/tools/platforms/hardware/BUILD
+++ b/tools/platforms/hardware/BUILD
@@ -21,6 +21,11 @@
 )
 
 constraint_value(
+    name = "cortex-m4f-imu",
+    constraint_setting = ":hardware",
+)
+
+constraint_value(
     name = "cortex_m0plus",
     constraint_setting = ":hardware",
 )