HackStudio: Add ProjectBuilder component

ProjectBuilder takes care of building and running the current project
from Hack Studio.

The existing functionality of building javascript and Makefile projects
remains, and in addition to it the ability to build standalone serenity
components is added.

If the Hack Studio project is the serenity repository itself,
ProjectBuilder will attempt building the component that the currently
active file belongs to.

It does so by creating a new CMake file which adds the component as a
build subdirectory.
It also parses all CMake files in the serenity repository to gather all
available libraries. It declares the libraries and their dependencies in
this CMake file.

It then uses the HACKSTUDIO_BUILD CMake option to direct the build
system to use this CMake file instead of doing a full system build.

Userland/DevTools/HackStudio/CMakeLists.txt

@@ -43,6 +43,7 @@ set(SOURCES
     LanguageClient.cpp
     Locator.cpp
     Project.cpp
+    ProjectBuilder.cpp
     ProjectDeclarations.cpp
     ProjectFile.cpp
     ProjectTemplate.cpp