ego now builds and is used.

This needed lots of refactoring to ego --- not all platforms have ego descr
files, and ego will just crash if you invoke it without one. I think originally
it was never intended that these platforms would be used at -O2 or above.

Plats now only specify the ego descr file if they have one.

plat/build.lua

@@ -20,6 +20,7 @@ definerule("ackfile",
 				"lang/pc/comp+pkg",
 				"plat/"..plat.."+tools",
 				"util/ack+pkg",
+				"util/ego+pkg",
 				"util/misc+pkg",
 				e.deps
 			},
@@ -67,7 +68,6 @@ definerule("ackprogram",
 				"plat/"..e.vars.plat.."+pkg",
 				"util/ack+pkg",
 				"util/led+pkg",
-				"util/amisc+pkg",
 				e.deps
 			},
 			_clibrary = acklibrary,