[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/tetratelabs/wazero/sys/stat.go

@@ -0,0 +1,107 @@
+package sys
+
+import "io/fs"
+
+// Inode is the file serial number, or zero if unknown.
+//
+// Any constant value will invalidate functions that use this for
+// equivalence, such as os.SameFile (Stat_t.Ino).
+//
+// When zero is returned by a `readdir`, some compilers will attempt to
+// get a non-zero value with `lstat`. Those using this for darwin's definition
+// of `getdirentries` conflate zero `d_fileno` with a deleted file, so skip the
+// entry. See /RATIONALE.md for more on this.
+type Inode = uint64
+
+// ^-- Inode is a type alias to consolidate documentation and aid in reference
+// searches. While only Stat_t is exposed publicly at the moment, this is used
+// internally for Dirent and several function return values.
+
+// EpochNanos is a timestamp in epoch nanoseconds, or zero if unknown.
+//
+// This defines epoch time the same way as Walltime, except this value is
+// packed into an int64. Common conversions are detailed in the examples.
+type EpochNanos = int64
+
+// Stat_t is similar to syscall.Stat_t, except available on all operating
+// systems, including Windows.
+//
+// # Notes
+//
+//   - This is used for WebAssembly ABI emulating the POSIX `stat` system call.
+//     Fields included are required for WebAssembly ABI including wasip1
+//     (a.k.a. wasix) and wasi-filesystem (a.k.a. wasip2). See
+//     https://pubs.opengroup.org/onlinepubs/9699919799/functions/stat.html
+//   - Fields here are required for WebAssembly ABI including wasip1
+//     (a.k.a. wasix) and wasi-filesystem (a.k.a. wasip2).
+//   - This isn't the same as syscall.Stat_t because wazero supports Windows,
+//     which doesn't have that type. runtime.GOOS that has this already also
+//     have inconsistent field lengths, which complicates wasm binding.
+//   - Use NewStat_t to create this from an existing fs.FileInfo.
+//   - For portability, numeric fields are 64-bit when at least one platform
+//     defines it that large.
+type Stat_t struct {
+	// Dev is the device ID of device containing the file.
+	Dev uint64
+
+	// Ino is the file serial number, or zero if not available. See Inode for
+	// more details including impact returning a zero value.
+	Ino Inode
+
+	// Mode is the same as Mode on fs.FileInfo containing bits to identify the
+	// type of the file (fs.ModeType) and its permissions (fs.ModePerm).
+	Mode fs.FileMode
+
+	// Nlink is the number of hard links to the file.
+	//
+	// Note: This value is platform-specific and often at least one. Linux will
+	// return 1+N for a directory, where BSD (like Darwin) return 2+N, which
+	// includes the dot entry.
+	Nlink uint64
+
+	// Size is the length in bytes for regular files. For symbolic links, this
+	// is length in bytes of the pathname contained in the symbolic link.
+	Size int64
+
+	// Atim is the last data access timestamp in epoch nanoseconds.
+	Atim EpochNanos
+
+	// Mtim is the last data modification timestamp in epoch nanoseconds.
+	Mtim EpochNanos
+
+	// Ctim is the last file status change timestamp in epoch nanoseconds.
+	Ctim EpochNanos
+}
+
+// NewStat_t fills a new Stat_t from `info`, including any runtime.GOOS-specific
+// details from fs.FileInfo `Sys`. When `Sys` is already a *Stat_t, it is
+// returned as-is.
+//
+// # Notes
+//
+//   - When already in fs.FileInfo `Sys`, Stat_t must be a pointer.
+//   - When runtime.GOOS is "windows" Stat_t.Ino will be zero.
+//   - When fs.FileInfo `Sys` is nil or unknown, some fields not in fs.FileInfo
+//     are defaulted: Stat_t.Atim and Stat_t.Ctim are set to `ModTime`, and
+//     are set to ModTime and Stat_t.Nlink is set to 1.
+func NewStat_t(info fs.FileInfo) Stat_t {
+	// Note: Pointer, not val, for parity with Go, which sets *syscall.Stat_t
+	if st, ok := info.Sys().(*Stat_t); ok {
+		return *st
+	}
+	return statFromFileInfo(info)
+}
+
+func defaultStatFromFileInfo(info fs.FileInfo) Stat_t {
+	st := Stat_t{}
+	st.Ino = 0
+	st.Dev = 0
+	st.Mode = info.Mode()
+	st.Nlink = 1
+	st.Size = info.Size()
+	mtim := info.ModTime().UnixNano() // Set all times to the mod time
+	st.Atim = mtim
+	st.Mtim = mtim
+	st.Ctim = mtim
+	return st
+}