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/cpp/gen_crosstool.py b/tools/cpp/gen_crosstool.py
index af28c56..547faf0 100644
--- a/tools/cpp/gen_crosstool.py
+++ b/tools/cpp/gen_crosstool.py
@@ -47,6 +47,13 @@
       '%NAME%': 'cortex-m4f',
       '%CPU%': '__MK64FX512__',
       '%F_CPU%': '120000000',
+      '%LINKER_SCRIPT%': 'motors/core/kinetis_192k.ld',
+      })
+  add_m4f_toolchain(crosstool_proto.toolchain.add(), m4f_proto, {
+      '%NAME%': 'cortex-m4f-k22',
+      '%CPU%': '__MK22FX512__',
+      '%F_CPU%': '120000000',
+      '%LINKER_SCRIPT%': 'motors/core/kinetis_128k.ld',
       })
 
   with open(args[2], 'w') as f: