Biggish refactor to break cycles; my build rules were full of them. cpm builds,

which requires top and topgen.

plat/pc86/build-tools.lua

@@ -0,0 +1,21 @@
+include("plat/build.lua")
+
+build_as {
+	name = "as",
+	arch = "i86",
+}
+
+build_ncg {
+	name = "ncg",
+	arch = "i86",
+}
+
+return installable {
+	name = "tools",
+	map = {
+		["$(PLATDEP)/pc86/as"] = "+as",
+		["$(PLATDEP)/pc86/ncg"] = "+ncg",
+		["$(PLATIND)/descr/pc86"] = "./descr",
+		"util/opt+pkg",
+	}
+}