Various C library adjustments

Fix weird linking issues with newlib:
- Get rid of dlmalloc
- Also get rid of klmalloc

Adjust crt0 operation:
- Kill the dead loop at the end
- Pass main to pre_main as a function pointer to move `main` reference
  into crt0.o

- Fix a build script derp with trying to remove build and local
  directories (gets rid of some warnings)