[build] first pass at multiarch support

Changing bonnibel to respect the --arch flag to configure. This requires
some reworking of modules, mostly in the addition of the ModuleList
class instead of just a dict of modules.

assets/build/amd64/config.debug.yaml

@@ -0,0 +1,9 @@
+---
+ccflags: [
+  "-g3",
+  "-ggdb",
+]
+
+ldflags: [
+  "-g",
+]