Make improvements

- Invent openatemp() API
- Invent O_UNLINK open flag
- Introduce getenv_secure() API
- Remove `git pull` from cosmocc
- Fix utimes() when path is NULL
- Fix mktemp() to never return NULL
- Fix utimensat() UTIME_OMIT on XNU
- Improve utimensat() code for RHEL5
- Turn `argv[0]` C:/ to /C/ on Windows
- Introduce tmpnam() and tmpnam_r() APIs
- Fix more const issues with internal APIs
- Permit utimes() on WIN32 in O_RDONLY mode
- Fix fdopendir() to check fd is a directory
- Fix recent crash regression in landlock make
- Fix futimens(AT_FDCWD, NULL) to return EBADF
- Use workaround so `make -j` doesn't fork bomb
- Rename dontdiscard to __wur (just like glibc)
- Fix st_size for WIN32 symlinks containing UTF-8
- Introduce stdio ext APIs needed by GNU coreutils
- Fix lstat() on WIN32 for symlinks to directories
- Move some constants from normalize.inc to limits.h
- Fix segv with memchr() and memcmp() overlapping page
- Implement POSIX fflush() behavior for reader streams
- Implement AT_SYMLINK_NOFOLLOW for utimensat() on WIN32
- Don't change read-only status of existing files on WIN32
- Correctly handle `0x[^[:xdigit:]]` case in strtol() functions

libc/intrin/kopenflags.S

@@ -36,7 +36,8 @@ kOpenFlags:
 	.e	O_TRUNC,"TRUNC"			//
 	.e	O_CLOEXEC,"CLOEXEC"		//
 	.e	O_NONBLOCK,"NONBLOCK"		//
-	.e	O_TMPFILE,"TMPFILE"		// linux, windows
+	.e	O_TMPFILE,"TMPFILE"		// linux
+	.e	O_UNLINK,"UNLINK"		// windows+unix
 	.e	O_DIRECTORY,"DIRECTORY"		// order matters
 	.e	O_DIRECT,"DIRECT"		// no-op on xnu/openbsd
 	.e	O_APPEND,"APPEND"		// weird on nt