Add platform mappings to make --cpu work again

Without using --cpu, changing the platform was resulting in a full
rebuild since the cache was per cpu, not per platform.  I'm sure there's
a way to handle this, but I know that adding a platform mapping will
make the caches work again.

Change-Id: I5b9a64e0cc27465b04e5991c2c1b3d9c6dea41e6
diff --git a/tools/cpp/BUILD b/tools/cpp/BUILD
index 4f0e6d9..ea25dd1 100644
--- a/tools/cpp/BUILD
+++ b/tools/cpp/BUILD
@@ -2,6 +2,17 @@
 
 package(default_visibility = ["//visibility:public"])
 
+cc_toolchain_suite(
+    name = "toolchain",
+    toolchains = {
+        "k8": ":cc-compiler-k8",
+        "armhf-debian": ":cc-compiler-armhf-debian",
+        "roborio": ":cc-compiler-roborio",
+        "cortex-m4f": ":cc-compiler-cortex-m4f",
+    },
+    visibility = ["//visibility:public"],
+)
+
 [
     cc_toolchain_config(
         name = "{}_toolchain_config".format(cpu),