* move stage2.cpp code into zig0.cpp for simplicity
* add -ftime-report and some more CLI options to stage2
* stage2 compites the llvm cpu features string
* classifyFileExt understands more file extensions
* correction to generateBuiltinZigSource using the wrong allocator
(thanks dbandstra!)
* stage2 is now able to build hello.zig into hello.o using stage1 as a
library however it fails linking due to missing compiler-rt
* remove dead code
* simplify zig0 builtin.zig source
* fix not resolving builtin.zig source path causing duplicate imports
* fix stage1.h not being valid C code
* fix stage2.h not being valid C code