This removes the implicit `-I libbcachefs` argument to $(CC), which in turn
requires a set of minor changes throughout the tools. There are two advantages
to this setup:
1) It is (arguably) easier to read, since the location of bcachefs includes
are easier to understand at a glance ("where does util.h live?")
2) It removes the need for a hack to include glibc's copy of
dirent.h explicitly via '/usr/include/dirent.h', because libbcachefs/
*also* has a dirent.h file and the compiler cannot disambiguate them.
This has some ramifications on systems where /usr/include may not
exist, such as NixOS.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
