Move the external file format stuff into its own module.

lib/external/build.py

@@ -0,0 +1,20 @@
+from build.c import cxxlibrary
+from build.protobuf import proto, protocc
+
+proto(name="fl2_proto", srcs=["./fl2.proto"])
+protocc(name="fl2_proto_lib", srcs=[".+fl2_proto"])
+
+cxxlibrary(
+    name="external",
+    srcs=[
+        "./ldbs.cc",
+        "./fl2.cc",
+    ],
+    hdrs={
+        "lib/external/ldbs.h": "./ldbs.h",
+        "lib/external/a2r.h": "./a2r.h",
+        "lib/external/scp.h": "./scp.h",
+        "lib/external/fl2.h": "./fl2.h",
+    },
+    deps=["lib/core", ".+fl2_proto_lib", "lib/data"],
+)