* 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