What language is used to build low level languages like c++ and java?
How could you build the first language with no language?
You don't build a language, but you build a compiler or an interpreter ... and for this you can choose any language even the language you want to compile ...
The first self-hosting compiler — capable of compiling its own source code in a high-level language — was created for Lisp ... Since the 1970s it has become common practice to implement a compiler in the language it compiles, although both Pascal and C have been popular choices for implementation language. http://en.wikipedia.org/wiki/Compiler