Add BUILD files for IMU board

Change-Id: I5437972c594ecd3ebeb24d9b9b96f2801b405021
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/tools/platforms/BUILD b/tools/platforms/BUILD
index 599f926..6e73a8e 100644
--- a/tools/platforms/BUILD
+++ b/tools/platforms/BUILD
@@ -67,4 +67,16 @@
     ],
 )
 
+platform(
+    name = "cortex-m4f-imu",
+    constraint_values = [
+        "@platforms//os:none",
+        "//tools/platforms/hardware:cortex-m4f-imu",
+        "//tools/platforms/go:lacks_support",
+        "//tools/platforms/rust:lacks_support",
+        "//tools/platforms/nodejs:lacks_support",
+        "//tools/platforms/gpu:none",
+    ],
+)
+
 # TODO(phil): Create something for "cortex-m4f-k22" builds.
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",
 )