Switch to a new cortex-m4 compiler

This one is newer, so it supports a newer C++ standard. It's also
hermetic.

Also add a variant for building for some Kinetis-K chips with less RAM
that are used on fet12v2.

Change-Id: I9e50b6aae498e0c35acfedb846b3ada619a0e630
diff --git a/tools/BUILD b/tools/BUILD
index 3f3d4b2..3a75af3 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -29,6 +29,11 @@
 )
 
 config_setting(
+    name = "cpu_cortex_m4f_k22",
+    values = {"cpu": "cortex-m4f-k22"},
+)
+
+config_setting(
     name = "cpu_armhf",
     values = {"cpu": "armhf-debian"},
 )
@@ -56,6 +61,8 @@
 
 environment(name = "cortex-m4f")
 
+environment(name = "cortex-m4f-k22")
+
 environment_group(
     name = "cpus",
     defaults = [
@@ -67,5 +74,6 @@
         ":roborio",
         ":armhf-debian",
         ":cortex-m4f",
+        ":cortex-m4f-k22",
     ],
 )