Instead of trying to build the host-side code generator helpers right
before we need them in the LibHTML build process, just build them ahead
of time in makeall.sh, like we already do for {IPC,Form}Compiler.
It's no longer possible to build LibHTML on the host machine since it
depends on LibGUI now. This patch gets rid of the dual Makefiles in
LibHTML since we only support Serenity builds anyway.
Also clean the code generator directory before building it.
This is a simple command that can be used to display HTML from a given
file, or from the standard input, in an HtmlView. It replaces the `tho`
(test HTML output) command.