fix regression of flock being called on wasi targets

* common symbols are now public from std.c even if they live in
  std.posix
* LOCK is now one of the common symbols since it is the same on 100% of
  operating systems.
* flock is now void value on wasi and windows
* std.fs.Dir now uses flock being void as feature detection, avoiding
  trying to call it on wasi and windows
01337e2093Andrew Kelley committed on 7/19/2024, 6:35:22 PMparent7157189
14 files changedLine totals unavailable