[mono] Create some dirs required for installation, to support bockbuild
[mono] Create some dirs required for installation, to support bockbuild

- Bockbuild installs msbuild to an isolated location first
- and later merges that with mono

- Our install scripts try to create links to `lib/mono/{x,ms}build/15.0`
but `lib/mono/*build` don't exist in the isolated location, so we create
them to help the installation.

mono/msbuild,mono/msbuild,mono/msbuild,mono/msbuild