Rename mk2rbc/cmd to make go install work properly

The standard go tooling assumes that a package's binary name should be
the name of the containing folder. Before this change, `go install` or
`go build` (without `-o`) names this binary `cmd`.

Test: treehugger
Change-Id: I45a4e97f4a0d59744d644e30636250ceefe3bd1c

mk2rbc/Android.bp

@@ -19,7 +19,7 @@ package {
 
 blueprint_go_binary {
     name: "mk2rbc",
-    srcs: ["cmd/mk2rbc.go"],
+    srcs: ["mk2rbc/mk2rbc.go"],
     deps: [
         "mk2rbc-lib",
         "androidmk-parser",

soong_ui.bash

@@ -33,8 +33,8 @@ export TOP=$(gettop)
 source ${TOP}/build/soong/scripts/microfactory.bash
 
 soong_build_go soong_ui android/soong/cmd/soong_ui
-soong_build_go mk2rbc android/soong/mk2rbc/cmd
-soong_build_go rbcrun rbcrun/cmd
+soong_build_go mk2rbc android/soong/mk2rbc/mk2rbc
+soong_build_go rbcrun rbcrun/rbcrun
 
 cd ${TOP}
 exec "$(getoutdir)/soong_ui" "$@"