[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/experimental/sys/oflag.go

@@ -0,0 +1,70 @@
+package sys
+
+// Oflag are flags used for FS.OpenFile. Values, including zero, should not be
+// interpreted numerically. Instead, use by constants prefixed with 'O_' with
+// special casing noted below.
+//
+// # Notes
+//
+//   - O_RDONLY, O_RDWR and O_WRONLY are mutually exclusive, while the other
+//     flags can coexist bitwise.
+//   - This is like `flag` in os.OpenFile and `oflag` in POSIX. See
+//     https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html
+type Oflag uint32
+
+// This is a subset of oflags to reduce implementation burden. `wasip1` splits
+// these across `oflags` and `fdflags`. We can't rely on the Go `os` package,
+// as it is missing some values. Any flags added will be defined in POSIX
+// order, as needed by functions that explicitly document accepting them.
+//
+// https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#-oflags-flagsu16
+// https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#-fdflags-flagsu16
+const (
+	// O_RDONLY is like os.O_RDONLY
+	O_RDONLY Oflag = iota
+
+	// O_RDWR is like os.O_RDWR
+	O_RDWR
+
+	// O_WRONLY is like os.O_WRONLY
+	O_WRONLY
+
+	// Define bitflags as they are in POSIX `open`: alphabetically
+
+	// O_APPEND is like os.O_APPEND
+	O_APPEND Oflag = 1 << iota
+
+	// O_CREAT is link os.O_CREATE
+	O_CREAT
+
+	// O_DIRECTORY is defined on some platforms as syscall.O_DIRECTORY.
+	//
+	// Note: This ensures that the opened file is a directory. Those emulating
+	// on platforms that don't support the O_DIRECTORY, can double-check the
+	// result with File.IsDir (or stat) and err if not a directory.
+	O_DIRECTORY
+
+	// O_DSYNC is defined on some platforms as syscall.O_DSYNC.
+	O_DSYNC
+
+	// O_EXCL is defined on some platforms as syscall.O_EXCL.
+	O_EXCL
+
+	// O_NOFOLLOW is defined on some platforms as syscall.O_NOFOLLOW.
+	//
+	// Note: This allows programs to ensure that if the opened file is a
+	// symbolic link, the link itself is opened instead of its target.
+	O_NOFOLLOW
+
+	// O_NONBLOCK is defined on some platforms as syscall.O_NONBLOCK.
+	O_NONBLOCK
+
+	// O_RSYNC is defined on some platforms as syscall.O_RSYNC.
+	O_RSYNC
+
+	// O_SYNC is defined on some platforms as syscall.O_SYNC.
+	O_SYNC
+
+	// O_TRUNC is defined on some platforms as syscall.O_TRUNC.
+	O_TRUNC
+)