Round 2 of c67b631 cleanup. After the dirent + utime fixes, the
MSVC link surface still had:
- LNK2005 'fopen already defined': dropped g_fopen so we no longer
override the SDK's fopen. UTF-8 paths still work on Windows 10
with the active-codepage manifest; non-Unicode codepages will see
ANSI translation. This is good enough for the public release; a
full UTF-8 fopen wrapper can be added later if needed.
- LNK2019 'unresolved S_ISDIR / S_ISREG': MSVC's <sys/stat.h> defines
_S_IFDIR / _S_IFREG but not the POSIX S_IS* macros. Add them in
the unistd.h shim (which main.c already pulls).
- LNK1181 'cannot open input file m.lib': test_merkle and test_rans
linked libm unconditionally. Math is in the default CRT on MSVC;
link 'm' only on non-Windows.
- 'unistd.h' not found in test_blockstore.c: it actually only needs
getpid(). Use <process.h> + #define getpid _getpid on MSVC, keep
<unistd.h> elsewhere.
87c5cf3b48